The UK opted out of many of the big European projects, and as a result people here do not have the same every-day experiences the continental Europeans have. No Euro, no Schengen. Still pay in good old British pound, still need to watch the exchange rates, always need a passport to leave the country. Paired with that the island location - no trains to reach bordering countries, no cars with other number plates, again, no foreign Euro coins to turn up in your change. The regulations, contracts, agreements happen far away from home and are not experienced directly and only reported in the media as 'the faceless bureaucrats in Brussels rule us'. Europe for most in the UK, is still something external, a holiday destination, not something to be part of.
There are other, underlying issues...a different understanding of democracy, the aspiration to be 'elite'....I don't think I could discuss this on here without causing a massive uproar, so lets just leave it at the bit above, which I think is a main reason of 'disengagement' with the EU.