Why is 'animal welfare' more common in EA than 'animal rights'?

well, I personally don't talk about animal rights because I don't believe in animal rights, and find the way most right discussions go bad and mind-killed. I also don't talk about right when talking about malaria in Africa! people don't have "right" to not be sick. I want people not to be sick and die, and willing to pay for that. 

I just generally don't look on the world using right-glasses, and don't find those googles helpful. quit the opposite. 

my question is the opposite - why do you want to talk about rights?  In my model, EAs tend talk less about right, because the sort of people who tend to become EAs tend to think less in framework of rights, and more in the EA framework. that the default EA reaction to sentence like "animals should have rights to wellbeing" should be "taboo the word right".

(I don't personally active in anything, i give 29.5% of my donations to Animal Welfare. and this is the name i use in a file that I created for myself, to describe the categories the way i think about them.)

Jeff Sebo's talk, "A utilitarian case for animal rights", is relevant to this. You can find a video and transcript here: https://forum.effectivealtruism.org/posts/u55MrNS3xvD4pf34m/jeff-sebo-a-utilitarian-case-for-animal-rights 

Summary: Utilitarianism, which holds that we ought to maximize well-being, is thought to conflict with animal rights because it does not regard activities such as the exploitation of domesticated animals and extermination of wild animals as, in principle, morally wrong. Jeff Sebo, a clinical assistant professor at New York University, argues that this conflict is overstated. When we account for indirect effects, such as the role that policies play in shaping moral attitudes and behaviour, we can see that utilitarianism may converge with animal rights significantly, even if not entirely.

Here's what I personally think about using welfare vs. rights jargon in my advocacy. These are some unpolished thoughts that I'm hoping to explore further in the future.

Pro welfare:

Some anti-incrementalist animal advocates try to gatekeep the term "animal rights". They frequently complain when incrementalist folks use the expression "animal rights". When I ask these advocates "What kind of empirical evidence would change your mind" sometimes I get the response "No biased study in this speciesist world would make me sell out my principles. Just like no evidence could convince me there could be merits to torture, I'm never going to negotiate on the basic rights of animals". This makes me react "Ok, in that case I'm not going to swear allegiance to your banner and I will grow what I believe to be good".

Existing animal advocacy is already heavy on rights. Focusing on welfare jargon allows me to raise a distinct banner, differentiate my brand and organise people who are more sympathetic towards welfarist thinking.

I'm happy with the philosophical welfarist tradition and their moral leadership on many issues. I want to signal continuity with that tradition.

Rights based jargon is in strong tension with non-violent communication. Rights based jargon invokes a frame in which some people are sinners and should be punished. I'm not sure how useful non-violent communication is. But if it's useful then it's better to avoid rights jargon.

When I look at the arguments themselves before taking peer disagreement into account, my first-order beliefs are very consequentialist. I think arguments against the significance of personal identity and arguments against the moral significance of act/omission or intend/foresee distinction are powerful and correct. As the main purpose of the communication is to make myself clear to the relevant stakeholders, welfare jargon is better equipped to make my beliefs clear.

Pro rights

Many people understand mere moral standing in terms of rights. Saying "animals have rights" is basically equivalent to saying "animals have moral standing" for these people.  So singling out animals by talking about "animal welfare" when the whole world talks about "human rights" might diminish perceived moral standing of animals.

In Turkish civil society, the term "rights based" is used to differentiate organisations that play by the rules of international human rights framework. I'm a huge fan of these norms and I'm happy to play by that book. Refusing being "rights based" because of my philosophical commitments would confuse people about where I stand in a political divide.

Since I take peer disagreement very seriously, I give significant credence to rights based theories and I'm not a welfarist. I also would like basic legal human rights to be extended to non-human animals. Avoiding rights terminology makes it harder to communicate this aspect of my thinking. 

I want to maintain that incrementalist animal advocacy and wild animal welfare work are actually compatible with a rights based ethical theory. By avoiding rights language, I fear conceding this framework entirely to anti incrementalist advocates.

I don't have an answer to your question, but this post from a few years ago might help build context and understanding.

The 2013 debate between Gary Francione and Bruce Friedrich was also quite illuminating  to watch (although I need to remind myself that just because one side is represented by a person who appears more composed or who is a better debater, it doesn't demonstrate that side's truth/accuracy).

[This does not represent the opinion of my employer] 

I currently mostly write content for an Effective Giving Initiative, and I think it would be somewhat misleading to write that we recommend animal charities that defend animal rights -people would misconstrue what we're talking about. Avoided suffering is what we think about when explaining who "made it" to the home page, it's part of the methodology, and my estimates ultimately weigh in on that. It's also the methodology of the evaluators who do all the hard work.

My guess would be that EA has a vast majority of consequentialists, whose success criterion is wellbeing, and whose methodology is [feasible because it is] welfare-focused (e.g. animal-adjusted QALYs per dollar spent). This probably sedimented itself early and people plausibly haven't questioned it a lot so far. EA-aligned rights-focused interventions exist, but they're ultimately measured according to their gains in terms of welfare.

On my side, I think it's already hard as it is to select cost-effective charities with a consequentialist framework (and sell it to people!), and "rights" add in a lot of additional distinctions (e.g. rights as means vs as ends) which makes it hard to operationalize. I can write an article about why we recommend animal welfare charity X in terms of avoided counterfactual suffering, but I'm clueless if I had to recommend it in terms of avoided right infringement, because it's harder to measure, and I'm not even sure of what I'm talking about.

I'd be happy to see people from other positions give their opinion, this is a strictly personal view.