I see what you're saying, but OTOH even without ads you really have no idea how much data you're using. It's just hard to manage your data usage in general.
In your settings on your phone you can click on Network & Internet, then click on Data Usage. However, there are have been studies literally showing that ads eat anywhere from 48% to 79% of people's data plans. It's hard to manage your data when your data is being used without you having any control over it.
Don’t go to websites festered with ads if that is your concern or install a web blocker.