I used AdBlock Plus for a while because it looked like the more popular ad-blocker.
I only uninstalled AdBlock Plus because it keeps displaying a "upgrade to premium" popup.
uBO has been such an improvement that now I worry I lost some geek gred for ever using ABP.
3-5% perhaps.
"Chrome is used by 3.45 billion internet users. That's up from 2.74 billion in 2019. Chrome has a worldwide browser market share of 63.87%."
https://backlinko.com/chrome-users
"Over 30 million Google Chrome users use uBlock Origin"
Source: the very article.
Even in the Google Chrome "niche", does 30 million out of 3.45 billion sound like 30-50% to you?
The overwhelmingly vast majority of human beings using web browsers are not using ad blockers. They wouldn't know how and it wouldn't occur to them in the first place.
I'm sure anybody would find it just as weird after they experienced an ad blocker for a short while, they just lack that initial impulse or idea that it's possible.