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Adblockers stop publishers serving ads to (or even seeing) 1bn web users - Press Gazette
(pressgazette.co.uk)
This is a most excellent place for technology news and articles.
Unfortunately I don't think you can just make it illegal. People/companies would still do it, just covertly. Then you end up in a situation where adverts are not marked as such and that's probably even worse than the current situation, where ads at least identify themselves as ads.