I think your characterisation of this as discovery is a little naive. What you are describing is a part of enshittification and it happens too often to be an accident. Revenue maximisation is always the end goal. Also it's not that the user is willing to pay with attention. There is no alternative. In fact it's the very opposite, more than once now a product has basically been pitched as "pay us to avoid ads" and then once it dominated the market they introduce ads. That's users trying to choose to pay with money over attention and ultimately being unable to do so.