Why girls don't sit with their legs open in the 1st place? If
they do so then guys won't be curious.
I think curious came from gals want to hide guys want to find out

we just want to see something that is not usually see in the open
area. I think usually we accidentialy swa it, and just kind of
curious to see the pattern of the bra and panties. Sometime it just
bouns to see more then just cloth maybe say nipple or pubic hair,
so normal reaction for guys to peep.