https://en.m.wikipedia.org/wiki/I_know_it_when_I_see_it
When Microsoft put live tiles and telemetry in Windows, whoever signed off on that knew they were crossing a line.
It doesn't need to be defined that strictly. The OP talks about FM radio adverts. An announcer telling you that a new song like, exists, could be construed in some sense to be an advert, just as my profile telling you that I am indeed a software developer could be.
But that's not really what's pissing people off and abusing their attention here.
I still think that definition is unworkable. What "the user wants to do" isn't even an objective measure. Is VIM malware because it includes s message urging the user to donate to charity, which is unrelated to it'd purpose as an editor? Is apt-get malware because it included an Easter egg? By that definition, the answer is both yes and no, since it depends on who is using it wanting that or not.