The primary thing is that they're there, that they make the world a worse with their nash equilibrium of "everyone is doing it so everyone must continue doing it", and that they're basically rich people begging you to give them more money. Outside of a context where you have made a conscious choice to spend money, at that.

I'd argue that even in a supermarket they're mostly useless and manipulative. I came in to buy bananas, you don't need to tell me doritos are buy 9, get 3 free.

Fuck ads.