That is literally the reason for which I finally canceled Spotify a few years ago. At that point I was accumulating reasons to switch for the last few years but that was the last straw.

I am paying your most expensive subscription and if you would have had a more expensive / premium one I would have paid more explicitly for the service to not include ads anywhere, under any possible curcumstance. Aparently that was impossible.

Never looked back and I should have done the switch years before.