I've never seen that. Not once.
Well, a few years back, Google sent out a notice saying that I was getting ads in my email. (whether I wanted them or not), and asked m if I wanted "targeted ads", or, I suppose "generic" ads. Since that time, I've always had 2 ads at the top of the page.
Now, I feel kind of silly, because I just checked and nothing was there
I do know, when the program was initiated, I tried to dismiss a couple of ads, and for my trouble, I was treated to a questionnaire.,
If you've never experienced this, consider yourself lucky, or I'm possibly hallucinating.
FWIW, I just went to my gmail account, and didn't find any ads.
Although, I would swear as recent as last month, I got a "targeted ad" from B & H Photo. which I did open, to see if duplicated my normal promotional mail from.them.
If you know anyone else wit an elderly Gmail account, consider asking them if they've ever experienced this phenomenon.
As for YouTube, if I watch on Firefox, I get loads of ads, whereas Opera blocks them altogether. (Which doesn't mean that Google doesn't still follow you around).