As a dog person, I always begrudingly wished the dogs would have participated in some sort of memewar. The cats got all the "aww cute" memes, while dogs got all the "herpyderp" memes.
But I guess that's why I like dogs more than dictatory, selfimposed, greater-than-thou cats.
...it depends on whom you ask, I think. For me it's for info/data exchange, wasting time, contacting people, shitposting. Roughly in this order of relevance.
Originally, to make the neurodivergent people of the world feel less alone. But then neurotypicals decided to monetise it and make it and use it for social engineering and data collection, so now we have nowhere again.
I remember the internet of the 90s before social media. It was really nice. Sure you had nasty stuff but you had to go looking for it. You spoke to people on niche forums and then added them to whatever messaging service you used. They new your name and you would occasionally send actual letters to each other or call each other on the phone. It was wholesome and good... This is not.