Likes/Dislikes allow people to express support without needing to provide any justification, and eventually a large amount of community support can look like evidence.It's not an avenue that encourages discussion, but it is a really good way to get a lot of safe, non-offensive posts to get a lot of attention, so it is real great if you are a fan of doggo memes, but not if you want a real answer.
I like that someone's ideas have only as much validity as they can provide for it, and if you can't articulate what you think then you don't get to express it. One of the main reasons I use this site is the lack of any sort of thing similar to a like button.
people have already said stuff similar to what's above but I can't upvote them