Apple needs to have an option to prevent that, but I'm more in favor of outlawing browser hijacking ads. This is worse than ads in paid programming (or apps ypu have to pay rather than get free).
I heard they were gonna make some kind of Adblock for Apple phones, I don't know when though. But yes those are annoying and why I use Adblock. It's alright if they are just around the page or a single one sometimes(cause you see it anyways) but I do not want them popping up every 10 seconds or 4 20 seconds ads in a short youtube video, jfc.
Yes they should kinda be forbidden, especially if you need to use internet in school/work/public areas since they don't want you to install things.. Regular ones are enough.