Because it works, and is a requirement to have a functional platform at all.
First, commercial speech is certainly speech. If you don't restrict anything at all, your platform will drown in a constant deluge of spam. So on that basis alone there's something you must remove if you want to have any kind of conversations happening, and therefore can't be an actual absolutist.
Second, there's illegal and just icky content. Posting pictures of poo isn't illegal. It can be "speech" after a fashion. That will also quickly result in people leaving.
Third, a free-for-all is only tolerable to a small segment of the population. HN for instance only works because it's moderated and curated. You can have something like r/worldpolitics which embodies the "no moderation" ideal. It's a subreddit where the moderators do the absolute minimum Reddit requires. Meaning it's mostly porn. And what's the point in having more than one of those? They're all more or less the same.
The problem is the algorithms that surface people's posts to those not friends with or following them. That's what turns a basic and true "social media" into a hyper-competitive arena which encourages a race to the bottom, to make the cheapest content possible to grab eyeballs.
"Social media" should not be a hyper-concentrated collection of advertising targets. That single aspect has probably caused 99% of "social medial ills.
First, commercial speech is certainly speech. If you don't restrict anything at all, your platform will drown in a constant deluge of spam. So on that basis alone there's something you must remove if you want to have any kind of conversations happening, and therefore can't be an actual absolutist.
Second, there's illegal and just icky content. Posting pictures of poo isn't illegal. It can be "speech" after a fashion. That will also quickly result in people leaving.
Third, a free-for-all is only tolerable to a small segment of the population. HN for instance only works because it's moderated and curated. You can have something like r/worldpolitics which embodies the "no moderation" ideal. It's a subreddit where the moderators do the absolute minimum Reddit requires. Meaning it's mostly porn. And what's the point in having more than one of those? They're all more or less the same.