There's a great video on this that was made when YouTube first started rolling this out called The Cobra Effect: Why Anti-Adblock Policies Could Hurt Revenue Instead, and one of the points mentioned in the video is the rising number of people who use an adblocker, and not specifically mentioned but shown in the video is a graphic from an article from 2015 which shows that just under 43% of people use an adblocker. That number will have obviously changed in the past 7 years, but if we just use 25% of viewers as an estimate, that's 25% of all viewers on YouTube who may turn to more "malicious" forms of adblocking such as things like AdNaseum and ReVanced or sites that host YouTube videos without the ads, and tell others to do the same if they're sick of ads. And even if they do give up and watch the ads, the science says that people who use adblockers are much less likely to click on an ad and make a purchase, which is bad for advertisers since they pay for the number of views an ad gets and their clickthrough rate would go down, making it more expensive and less profitable to do business with YouTube.

https://www.youtube.com/watch?v=gIHi9yH6UB0