Because it's where their friends (or something like) are.

There are options, but in order to have uptake, they have to prove that they are better in most ways by getting people to switch. It's the credit problem all over again.

I'd switch in a heartbeat if 1) I had a pressing need (I don't) or 2) if I knew anyone on one of the other networks (I don't).

That doesn't even cover the technical issues in switching. Hosting your own Mastodon instance (for example) is pure arcane witchery for most people and if they just want to join a pre-made instance, well, see above. That's not to mention the additional load of actually using the thing.

People have had a lot of time to get used to FB. Its not like the old days when all of them were in their infancy and not many people were joined up. You could switch then without any major repercussions and all of them sucked from a usability standpoint.

FB won by just outlasting everyone else.

They feel secure in the knowledge that the records coming from banks and hospitals will be anonymized for their protection.

serotonin hit