In Game Lobby, except actually on the main menu.

You can't join a game, because you're "already in a game lobby". You can't select your champion, because you're "actually on the main menu screen."

You're now penalized, because you didn't select a champion, because it was physically impossible for you to do so, and now you must wait 30 minutes to join another game, because you delayed a match for 9 other individuals.

Cough Horseshit cough