Well I just read a few posts on the first place which included the lines like, "...men do it [after finishing their piss] for women, etc.."
I just don't understand how are we supposed to know whether a woman is gonna be the next to use it?
I think its done because of the ratio 3:1..... it has to be lifted up only when man need to piss, but in every other of the 3 cases (man shits, woman shits, woman pisses....sorry for any offense) it has to be kept down.
So maybe its done because majority 'tasks' are performed keeping it down.