We may not be in the EU any longer, but if we want to sell bottled products into the EU we have to abide by their regulations. It's much more cost effective that manufacturers having to have two production lines, one for export goods and and one for local consumption.
We also abandoned any attempt to have our own quality assurance mark for much the same reason and have reverted to the CE mark.
It's one more instance of the futility of Brexit really.
I don't find tethered bottle tops a particular problem, but if folks feel the need to cut them off it seems like a reasonable solution. I expect some people in the EU do it, too.