It sets the mood. Though it might look suspicious, fifty students all meeting in the same girls' bathroom, and moaning myrtle could tell someone. Also the room magically supplies itself with the stuff they need.
Everyday of my life, all the time. <--- Same here, except that I'd like to be the professor teaching Muggle Studies. Suddenly students are skateboarding to classes and Indoor Quidditch has been invented by using parkour skills instead of brooms.