Preinstalled ad-blocking would probably decimate what is left of quality media landscape within a few years. I'm quite happy if it requires at least a tiny bit of effort from the user. Some people simply don't mind ads, and we should all be grateful to them.
(I'm using uMatrix and try to allow all non-terrible ads on quality sites)
There is already a browser that ships with built-in ad blocking: Opera.
Although, as it's less known than others and it has no Microsoft or Google shoving it in users' faces, I guess you could count finding and installing it as "effort".
(I'm using uMatrix and try to allow all non-terrible ads on quality sites)