This is the result of a simple equation:
The more time you spend on an online website/app the more ads they can show you. And with that, the more info they make from you, the more relevant the ads become, and the more money they make.
Keeping you glued to their website or app is the goal of "free to use" social media apps.
If i had no ethics, and corporations as naturally amoral entities don't, i'd hire PhDs in psychology in order to try to employ tactics to keep you engaged and spending as much time in the app as possible. This, btw, is exactly what they have been doing.
Tiktok became super big in western world around the time of covid, and that one was the first app i immediately noticed how stupidly addictive and "brain rotting" it was. Soon after Instagram introduced Reels, Youtube Shorts, and Facebook their own shorts.