I'll give Riot the benefit of the doubt and just assume they don't know about this...

There is a MAJOR issue with custom games that affects every player attempting to find an appropriate game lobby. In the disorganization and chaos of the custom lobbies, players create custom games and fill them with bots in order to have the lobby appear more full, stay at the top of the list and trick players into joining.

This can be VERY QUICKLY and VERY EASILY solved by the addition of a filter box that allows a player to ignore lobbies that contain bots.