Companies are becoming even more greedy recently across the board and at a rapid pace. Some people would want you to believe Youtube wouldn't generate billions of dollars as income annually for Alphabet for some reason. But the truth is the platform is extremely profitable already. Youtube simply wants even more now because competition has done the same. We've seen prices spiraling up and quality dropping in pretty much all sectors of the economy and this trend will continue for the forseeable future.

In short: Because they can (some are really stretching their boundaries, though)