Because they don't keep it confined to the bedroom. The chances of getting buggered over the bonnet of your own vehicle are significantly increased with them attending meets. Passenger rides? No thanks, Christ knows where there gearstick has been (it's why you have to buy new cars) and the thought of being violently fellated at 120mph on a lonely moor road gives me a funny feeling in my tummy. Then two hours in a pub talking about The Wizard of Oz with appletini's all round, with a looming Dolly Parton karaoke is not everyones idea of a good time.
That said, to each their own. Not a fan of the moustaches, prefer if they all had badges or something instead.