I know quite a few younger people who drink real ale, myself included (CAMRA member here too).
That said, transmanche isn't entirely wrong with what he says. I've got plenty of friends or acquaintances who won't even contemplate it as an option. A big reason for this is that they grow up with Carling, Carlsberg etc via advertising and so when they first manage to get served in a pub and they know bugger all about alcohol, that's what they go for. Indeed, I think I was the same in those early days. I mean, there's this guy I know, who's 21 but mentally about 12 and he drinks Corrs Lights. Free country, of course, but I know for a fact that he only drinks that (which tastes like carbonated water to me) because of that daft Jean-Claude Van Damn advert.
Also, most young people drink alcohol to get smashed. Real ale suggests that the drinker may actually like ale and that's the reason they go out, rather than get smashed and hopefully wake up next to someone who you'd wan't to wake up with.
In the end, real ale still instills to impression of seriousness and old people. This is like what garlic is to a vampire when it comes to the 'lets get smashed, puke on the pavement, whilst exposing our panties to the world' contingent that you get. And that's the whole point of participating pubs refusing to sell lager and shots on this trail.