One consequence of the UK being a very stratified society (it's both a symptom of low social mobility, and in turn an ongoing cause of same) is that people here tend to be very sheltered - MNers in particular. (Sorry I'm not trying to be mean, I'm calling it as I see it, like the brash foreigner I am
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So there are MNers who think it's normal not to go abroad for ten years. There are MNers who feel like poor church mice because their mates at Oxford went into banking when they became teachers, and now they are trying to raise 3 children in a 2 bed in Zone 5. There are MNers who are from the Jilly Cooper style old fashioned country UMC/UC of battered Labradors and stinky Volvos. There are MNers from the London seriously wealthy, where half their colleagues and social circle in the bank and St John's Wood/Chelsea are not British at all but national identity is almost an antique irrelevance in a world where they could be transferred to New York, Frankfurt or Geneva at any time.
Likewise there are MNers who never meet a non-white person from one week to the next, and MNers who consider a school with less than 40% non-white-British ethnicities to be alarmingly undiverse. MNers where everybody they know has completed their family by 25, and MNers where marrying, let alone reproducing, before 30 is a bizarre and self-destructive life choice.
And I hasten to add, none of these people are bad. Or at least, lots of them are bad and lots are lovely, helpful, annoying, clueless, judgemental, generous. They are all just human. I'm not trying to suggest that any one of these ways of life is inherently superior or inferior. (Though I would say that among the many downsides to such a stratified and divided society is that it fosters hostility and judgementalism between divergent groups.)
So many British people live in bubbles. It's the case in other countries too of course (an accessible example is the extensive discussion of the past two years on Trump Country etc) but it's particularly bad here. I think the most worrying sign is that the division and hostility only seems to be increasing while social mobility continues to fall off a cliff.