Why have American sports nutrition manufacturers like EAS left the UK market?

EU regulations are certainly unnecessarily strict. Dozens of harmless vitamins and minerals which have been used for decades without any reports of negative effects have already been banned.

Also, soon only product claims which have been passed by the European Union will be allowed on product labels and in advertising. So even if your product claim is entirely factual and not misleading to the consumer, unless it has been specifically applied for and granted by the EU using their inappropriately strict pharmaceutical standards of evidence, you won't be able to make the claim.

So this didn't exactly thrill EAS or most other companies who sell in Europe (no matter what country they are based in) but I think the reason that they left Europe is that their long-term strategy of spending a lot of money to get their products into the mainstream (and not just to sell to dedicated gym-goers) wasn't working despite pumping a HUGE amount of money into it. Despite being owned by a pharmaceutical company with deep pockets, at some point, if your strategy still isn't working, you have to pull the plug.