they want to sell ur email + metadata to data analysis corps so they can sell that aggregate info + analysis to other corps (associating email/identity with specific interests for marketers etc.)

Account registrations are one of the top-line key performance metrics these companies show to their investors to demonstrate they are growing. The day people stop signing up for these websites is the day people stop investing, and then they are in deep fucking shit. They juice these numbers any way they can. Dark patterns like this, lax enforcement against bots, etc. When the well of posters dries up, they have no choice but to squeeze the lurkers.

They have been focusing on growth at all costs for years, but because the VC money is drying up and they need to actually become profitable they're trying to find a way to turn inactive users into revenue.

Unrelated, but I do get mildly annoyed at friends who send links to fb and ig instead of the image. Like come on, you gonna make me make an account?

If they can’t use third party tracking cookies and they respect do not track and you have ppa turned off then they’re just not fucking gonna let you see their shit unless you make an account and give them some way to advertise to you.

The internet is television with even more ads and tracking. You have to either pay to not have it happen or actively take part in an arms race against it or some combination of both.

To pump up their numbers so they can tell investors they have a ton of "active" users.

Meta's business model is about collecting user data for advertisers. All of their services are a means to that end.

What everyone says doesn't completely answer the question. Yes it's about selling your data and attention to advertisers. But if it's about the "meta", than there is a twofold strategy about it: first exploiting the network effect (wikipedia link) while growing. And then locking in the market ("keep you in their ecosystem"), thereby locking out competition. It's ironic, but capitalists hate competition (in their own field) so much they would do everything to avoid it.

Their ideal endgame is what Amazon has achieved: becoming so big, they can start selling other capitalists access to their walled in market.

All these platforms could have been made compatible with each other (like federated instances). Without content walled in behind logins, we would be able to put together our own feed with content from all over the Internet and choose our own algorithms to sort it. But then no one could sell your attention or data to advertisers and small creative upstarts would be able compete with big entrenched content providers.