Britain has never really considered itself part of Europe, they've historically taken amusement in the irony of how they refer to "Europe" and "the continent" to refer to not the UK, as though they're not part of it. They don't learn the languages of Europe more than what's needed for a vacation, at best. They didn't join the EEC, which certainly looked a lot like they wanted to use their pound sterling more than to help the community. And now of course Brexit, which makes no sense at all from a rational perspective.

The argument of doing what's best for everyone is just not something that resonates in their politics, much in the same way that's it's not a mainstream value in the USA either. Rather it's about "what's in it for me". Those are not the values of the majority in continental Europe thankfully, asking the question of what's best for everyone resonates stronger.