I can't play your game because I have noone with which to play it. Which pretty much sums up the problem with indie multiplayer games.
A lobby would help. Local multiplayer (multiple players on the same computer) would help. A single-player mode would help. But a multiplayer needs a certain minimum popularity in order to survive at all. A single player game can survive as long as at least one person wants to play it, but a multiplayer games needs at least two people who want to player the game at the same time with each other, and these people need some way to find each other.