I don't mind that question, and I answer honestly when I do get asked it. I had a crappy job and I wanted to do something more fun that paid the bills without needing to go to uni.
I really don't like clients who ask how many I've seen that day, if I've been 'busy', how much money I earn in a week, how many men I've had sex with, or who want lots of personal information (they notice the ring and think it means they get to ask where my fiance works and what his name is!). I mean, I'm pretty open and share a fair amount if asked, but there are limits!
I used to mind it but I think ranting on SAAFE about stuff actually makes me less uptight so I'm not fussed anymore. I used to particularly stress about *why* they were asking - do they really want me to roll about on the bed telling them I LOVE fucking I'm SUCH a nympho I just can't get enough?! It would be annoying if they did (and they wouldn't get any such amateur porno-talk from me, lol, it makes me do snorty-laughs) but actually, I think most clients are honestly interested in just the same way any other average person would be. Or even if they are very used to being on the punter side of the sex industry, it's still very common to ask anyone doing a non-menial job how they got started.
Another thing is that they could be asking to try to check that there aren't any "she's trafficked ahhh!" clues, but again, if things seem great and you seem independent/happy from the start then they probably wouldn't ask out of anything more than idle curiosity. Probably on the off-chance that you do suddenly remember that it's cos you're a TOTAL nympho and can't control yourself around cock, too.
Some of the advice I was given ages ago here was to think of it as a fun opportunity to make up an entertaining story. You're not going to be able to undo a lifetime of social conditioning and convince a skeptical punter that you really do enjoy 99% of the job (I swear they all secretly think they're your best-looking client and that when you're not seeing them, you're sucking tiny stinky willies attached to obese hairy troll-men instead
) so I tend to be just honest about the ups and downs and a bit of my personal experience (ie that it's not the career for me permanently but it's been brilliant for the past year and probably another year yet!) but nothing too deep.