Yes, it really is so foreign! If your family has never even had a dining table (tiny galley kitchen) and eat off laps on the sofa, using a fork only, then a massive row of different sized knives, and everyone looking to see how you use them, is daunting.
SubFusc, scout, battels, Michaelmas, don, gaudy, proctors, tripos, exeat, and other obscure language ad nauseam. 
The highlight of the social calendar being a May Ball, with a ticket price higher than a family week in Butlins.
Secret and closed societies being common. Cardinals, Apostles, The Bullingdon Club.
And if you come from a minority background and already feel that you fit in only by hanging in by your finger nails, and if you have come home from school on a bus where the private school kids from Dulwich schools refer to Comp students as 'peasants', or you go to a Croydon state school where the neighbouring private school shout 'chavs' during rugby matches (as reported in the Evening Standard), then yes, you might well find it off putting.
My Dc have potentially Oxbridge-worthy A level predictions, but having been in a diverse S London comp they are not so much outfaced by the arcane traditions as disgusted by the perceived snobbery and elitism. I am trying to get them to see past that and have more open minds.