Sure, advertising is profitable. Yet, there are various regulations or social norms telling what is available and what is not. For example, we can think of covering a landmark "because it is profitable" - e.g. think of dressing the Statue of Liberty in clothes of a given brand, or covering the Greek Pantheon in free-to-play game ads.
Of course, tastes matter. The US is littered with (in real world) advertising banners, my native Poland - even more. But there are quite a few places in the Europe in which people would consider it off putting to use a glowing sign on a historical or otherwise clean design.
So it is about both tastes and regulations.
> most people are reluctant to spend money, but they're ok to "spend" their attention and their data
This is a tricky part. Kind of miss times when we were buying paper newspapers.
But let's take an example - devs were reluctant to pay $ for services. Not everyone and their dog pays for tokens.