Creators on YouTube do it for monetization. There are now multiple generations of youths for which “influencer” is their desired career. If you make it, you make it big.
They might pull in more money with sponsorships but they only got there because the algorithm put them at the top where the money is.
Don’t believe me? Look up the woman who shot up google HQ when they demonetized her channel.
I know someone who got addicted to the influencer money in Tiktok and dropped out of a med school program because making 5 figures a month, taking videos of you wearing fancy clothes was way better than slogging thru med school