Despite what a lot of people (include me) think of the EU, at least its member states operate under one set of regulations, which means anyone selling to the EU only need to pass regulations once. Realizing that goods trade is so important inside the EU, that's why multiple member EU states are spending a fortune on initiatives to improve trade, especially train transport (they're building two major tunnels for rail transport from Austria south and massively improving railways in Slovenia, Croatia and Serbia).
yes, it has trade advantages - i was only pointing out the oddity of claiming brexit was the reason ‘conservatives’ were losing when their electorate seems to be moving away from their failures and to the people who led brexit and want tighter border controls.
“at least its member states operate under one set of regulations”
I have relatives who live (or have lived) in various EU countries and conducting business across borders does seem to be straightforward for them.