Often lobbies take a while to fill -- sometimes reaching 45min-1hour. In these instances, lobbies have a harder time to fill often due to players becoming bored and leaving.
A solution to this is to allow players that have joined the lobby to "pre-join" the server -- this allows players to participate in Soap DM, jump around the map, practice role-outs, etc.
This would encourage players to remain patient to play in the lobby, hopefully increasing the number of successful lobbies.