I saw this in r/AssholeDesign:
A user in the comments verifies that Yahoo and Gmail do it too. In the case of Gmail, in the promotions tab:
I’ve never seen it. Not sure why. Maybe because I pay for Gmail storage or something and that makes me a paid customer and they don’t show them for paid customers? Can’t confirm.
But I can see why users would be kind of up-in-arms about it. People that take care of their email, count me included, spend so much time making sure that place is clean. No extra crap in there. Seeing an ad right in the inbox area is like seeing spam slip through, or something you unsubscribed from not respecting that. Real thorn in the side.
I can’t totally blame them. The web is largely monetized by subscriptions and advertising so if you aren’t paying for a subscription, advertising it is. If I started getting that in Gmail with no fair way to turn it off, for the first time in my life, I’d start looking elsewhere.