For the same reason reddit became what it became. No matter how hard anyone on reddit tries, people are going to continue using up/downvotes to roughly mean "like/dislike" or "agree/disagree". ignore/mute/hush are a hell of a lot more powerful than a single like/dislike, and people are going to use them to simply mean "I don't want to hear your opinion anymore". And they already do. The reason those of you who have been here longer don't experience it to the level that the new people do is simply because you're dealing with people you're familiar with, and those people are less likely to mute you for your opinion than someone they are unfamiliar with. That's just how people work, but it's not an environment where a lot of good discussion can take place. As much as people complain about reddit, I've experienced more blatant censorship of my thoughts on this site than I ever have on reddit.