There's a caveat there; Google is very incentivized to keep around any service on which it can display those ads! Gmail isn't going away any time soon in large part for that reason.
> When you open Gmail, you'll see ads that were selected to show you the most useful and relevant ads. The process of selecting and showing personalized ads in Gmail is fully automated. These ads are shown to you based on your online activity while you're signed into Google. We will not scan or read your Gmail messages to show you ads.
from this page:
Edit: I have noticed adverts depend on how your access Google e.g. I found the iOS YouTube app way worse than the website in the browser.