because advertisment companies pay content creators either directly or indirectly, and many people stick around platforms to watch their favourite content creators. being funny online has become a day job for many, and with the job market being the way it is being an "influencer", even if a niche one, pays better than a "real" job.
i'm not trying to excuse anyone here, it just is the way it is. do i like it? not really. but i also wouldn't want people who make a living working as "online funny person/influencer" to suddenly lose their income. if we got rid of ad companies a lot of things would have to change at the same time for nobody to get hurt in the process.
when i stop being broke i'm going to sign up for nebula, that place seems to be trying to change things for the better in this regard