I could be wrong but I was under the impression that ads paid primarily per click, in which case surely the relevancy is important too?
Even if you pay-per-view of an ad, a company selling tampons will not pay as much for 1 thousand views of their ads on a youtube channel for construction workers, as on a youtube channel for girl's fashion. Because the former drives no clicks/revenue, and the latter does.
So yes relevance is extremely relevant to make money.