Cultures and traditions are always being lost, everywhere - it's progress, plus some of them are bad - like the house of lords, casual racism, hunting, slavery and only eating boring food and weak beer.
As for 'Britain traded freely before hand' - are you living on cloud cuckoo land? there had to be hundreds of continually shifting trade deals with every single country individually, there were tariffs, import duties both ways, political bargaining and bartering, it was a nightmare for businesses who trade abroad. Also, countries in the EU get to benefit from preferential trade deals that only a political entity the size of the EU could negotiate, that was one of the main points of it.