@Goldenzeal
Youtube operates at a loss and is held afloat by google pumping in lots of money. And they're not doing it to be nice, it's still a huge platform which they can use to boost the awareness of other projects they wish to promote. It also allows them to push their own ideologies and narratives by selectively enforcing content rules.
Ads are one of the reasons why youtube has gotten worse and worse over the years, they begun bowing down to big companies that only want ads on maximum family friendly videos which has caused them to censor people (both via manipulating search results with their algorithm and constant rule changes to stop certain content) and dissuading them from uploading interesting content.
If it weren't for advertisers they'd have no reason to not permit all content besides that which breaches US federal law.
Ads aren't necessarily a bad thing but many businesses make adjustments to accommodate both the ads and advertisers, this leads to a worse end product which is objectively a bad thing.
For the consumer they're at best a minor annoyance but can be much worse, such as video ads which steal your free time or ads which are injected with malicious code.