I assume it's because they know they are going to get the best possible treatment that they either wouldn't get through the NHS or would have to wait yonks for.
I remember a bloke on there once who had a constantly smelly bum. The solution turned out to be that he just needed to wipe his bum better and more often.
I've also seen people who have been to their Docs but got nowhere.
I remember one little girl a few years ago who suffered from extreme varucas (sp), it was awful. They overtook her entire feet and looked so painful. She'd been to her doctors seversal times but nothing had worked. EB sent her to have some tests and discovered she had a potentially very serious condition (blood I think) and the varucas were a symptom. They were then able to treat the condition and it's symptoms improved vastly. I cried watching that poor little girl who was suffering so much but just tried to not moan about it.
And lets not forget the woman who was addicted to giving herself coffee enemas every day. And washing the tube in her dishwasher with all her food dishes. Bleuugghhh!!!
but some of them i've seen, they have been suffering for years and this is the only way they have managed to get treated effectivly. - the guy with the open abcess in his backside, he's put up with that for a few years!