I think it's this simple.
The EU is basically the creation of a USA/USSR (big, big state) in Europe. It's great for people who think that their own country is run by inept politicians and would therefore rather be ruled over by those much more sensible European politicians and have safety in numbers. However, many people would much rather run their own business and take their chances on the success or failure of that business based on their own efforts (small state). Many of us just do not want layer upon layer of rule makers telling us what is good for us, we can decide that ourselves.