Humans by nature ( look at other social media) post 99% useless bullshit. If we give them the feeling they are not welcome, simple they avoid hive.

No user experience = no growth potential = meh investment.

Most people don't care about a 1-5 cent upvote. But they care of a downvote and the feeling behind it.

There are studies around that topic.

To keep it simple, the user must like the feeling to be here.

Edit: and to point 1. If it would be decline by default = user experience ok. If not you show people disagreement. This is nothing people accept in 21 century.

Even a man that's becoming a woman is today a woman. Disagree with it? People cancel you.