If you think that the only thing required to run services like Facebook and Instagram is a supply of content, by all means, make your own platform. But you'll pretty quickly discover that developing the infrastructure required to handle hundreds of millions of people uploading hundreds of gigabytes of data every minute isn't actually a trivial problem, and that there's a reason Facebook pays hundreds of engineers a lot of money. Meta's labor costs, excluding sales, marketing, and admin, were 15 billion dollars in 2022. Just keeping the lights on for service as that scale is not a simple task at all, let alone actually building anything new.

If you want to get content from your friends, the postal service is perfectly well-equipped to deliver that, or you can of course simply meet up with them in person. But if you want a platform with essentially everyone you'll ever meet on it that's capable of hosting and sending almost any content you can imagine instantly for free, that does actually take money to build. Undoubtedly, there is some money that's siphoned back towards investors as well, but their products also wouldn't exist at the scale they do now without the 26 billion dollars of debt that they also have right now, which obviously needs to be re-paid.

I get that you're probably not actually looking for answers to those questions, but my point is that they do have answers if you actually cared. Again, if you don't think they're actually providing any value, then do the obvious thing and don't use them. After all, by your own position, they're not actually providing anything, right?