"Why should I trust a bunch of randos with it? Why should I give them my password? […]"

lol that right there you should respond no one should have your PASSWORD (singular) to begin with. Companies large and small have data breaches all the time. If the same password is on more than 5-10 sites, you should assume it's been compromised by now, and explain that they need a password manager.

Far as it goes with professional companies, we are talking public posting social media, the differences between them are all public, the biggest thing is what they chose to censor. Twitters cool with letting nazi's speak, but censoring the left. Most lemmy instances are the opposite, but there even are lemmy instances that are backwards with that.. which is the point. We all have differing oppinions on where the line should be drawn on acceptable speech, Being able to custom pick one of 50 groups is more likely to find one that works for you, than picking one of 3 social media giants that will have their own rules.