It's worth noting that YouTube have both a blacklist and a whitelist for advertising. Most videos that get "demonetised" are still eligible to earn ad revenue,

It's worth noting that YouTube have both a blacklist and a whitelist for advertising. Most videos that get "demonetised" are still eligible to earn ad revenue, but advertisers have to specifically opt-in to advertise against these videos. A small proportion of videos and creators are completely ineligible to earn revenue because they explicitly violate YouTube's ToS (usually on copyright grounds). Channels also require a minimum number of subscribers and views to be eligible for monetisation. This strikes me as a sensible compromise. Most content creators are frustrated by the lack of transparency and the often arbitrary nature of demonetisation, but they see it as essentially necessary to safeguard their livelihoods. YouTube didn't start demonetising videos apropos of nothing, they did it as a specific response to an advertiser boycott in 2017. To a great extent, demonetisation saved YouTube from economic failure.