Why is 'girl' different from 'boy'?

[Jessica2point0]

When used to describe adults I mean. I was in a doctor's waiting room this week and the receptionist said to another member of staff "will you tell Dr Jones that this girl is here to see him?" It got me thinking - if DP (same age - 29) was in a waiting room I really don't think the receptionist would have said "will you tell Dr Jones this boy is here to see him?" And now I'm irritated by the fact that it's okay to call me a 'girl' but not okay to call him a 'boy', but I don't know why. Any ideas?

because it's patronising and sexist. as you say, you wouldn't describe a 29yo man as a boy, because he's an adult. yet women of almost any age can be described as a "girl", as though she isn't a fully-grown adult

Thanks Hap! I think its the patronising bit that really got to me, though I couldn't put it in to words. I was confusing myself cos I don't mind being asked for ID buying wine (not that it happens often these days), but I suppose that's different because the cashier has to be sure of age so doesn't really have a choice, whereas the receptionist could easily have used 'woman' instead.