I think it is occupational ease more than anything else in marketing. Having to deal with the actual details is 'boring' even if it is relevant and advertising is all about what sounds good instead of actually being good. That is a widespread issue with society in itself and trend following. And metric-itis operates based upon things like 'was the ad or brand remembered' as opposed to 'did it actually improve sales'? You get what you measure for.

As for being okay with it the whole thing falls into tautology logic - it works because it works until it doesn't. If people actually cared enough about relevance than the problem would take care of itself by being absolutely useless.