Everyone is telling you about the algorithm punishing any non-sanitized content, but I'd like to present a slightly less worrying reason why people do it: to avoid getting harassed by chuds searching for topics like 'rape' and 'nazi' and starting arguments.
I think there is a lot of Mythos surrounding "the almighty algorithm" and getting fewer views on posts containing words advertiser's don't want associated with their products.
Lots of people get in the habit of doing that if they are content creators as depending on the platform you can get demonitized or have your video quietly suppressed. Most of this happens automatically by filters or transcriptions, and is opaque to creators so its hard to tell what is allowed. So if you are an Instagram creator or youtuber you can build the habit of preemptively censoring words you think might get flagged.
This trickles out to content consumers as well though - some of my younger friends always do these replacements everywhere, and they're definitely not a content creator. Exposure to a speech pattern will inevitably influence your own.
Please note I'm not passing a value judgement like "kids these days", just pointing out that not everyone who does this is a content creator.
Self-imposed 1984 type of stuff, right there. I don't get it either. Makes me feel like we're pulling ourselves into some crazy pants alternate reality
If by "some" you mean The Algorithm™ on corporate-owned (read: advertiser-subservient) social media, apparently yes. Now that I've put it that way, is it really that surprising?