When you go to the cinema, you are intending to watch a movie. Before you go into the cinema you see them selling popcorn, you want popcorn, you buy the popcorn. You go into the cinema, then an actual ad plays on the cinema screen before the movie.
This is the distinction. What you think of as an ad, no one else does. That’s all. You think something is an ad. The rest of us totally disagree. You think anyone listing things for sale outside of a dedicated and importantly separate space is an ad. The rest of us totally disagree.
I understand you now, but your idea of an ad is absolutely not the same as everyone else’s.