YouTube is currently rolling our a trial subscription service that allows viewers to directly pay content creators. It seems this is a reaction to the significantly increased presence of Patreon in this space.
Based on comments made by some creators in their videos it seems that in the last year YouTube have been making regular and cumulatively significant changes to their monetisation algorithms that increasingly favour short, high traffic, "clickbait" videos. Reading between the lines this suggests that these type of videos are what make the most money for YouTube so that's what their algorithm is being trained to favour: advertisers are the most significant monetisation channel so that's where users' attention needs to be directed.
Whilst this is good at optimising the adversing revenue it's not good at optimising content quality so, as the quality goes down, the number of views needs to go up which would adequately explain the steady descent into the clickbait swamp typical of the advertising funded attention economy.
Patreon has tapped into the resultant gap that has been created and given consumers the chance to directly reward creators and provides a different, although more traditional, direction for incentivisation. The fact that YouTube is now hurriedly responding to this with an internal version of the same feature shows that they clearly see this as a threat to their revenue which, until now, has been entirely based on advertising.
This is a classic demonstration of how defining success metrics define a product. You can have a product that's highly optimised for one metric and performing extremely well but if it's the wrong metric then you're ultimately harming your business. It takes intelligence to optimise but wisdom to know what to optimise.