It does happen, although quite rarely that all tables are taken and there are still people who want to play, but I think it'd be better to have a table for 4 players and no one would wait.
I don't know how it is built and I'm not much of a programmer, but could someone who is or is directly involved in GCCG program, tell us if it's possible to make tables work for 2, 3 or 4 players, depending on the demand. The way I see it, it could be done, just add another option to make the game start when all players are ready (the way it is, first 2 players would only play). Of course, tables would need some modifications, but as I said, the way I see it, it can be done, but I'm no expert.
However, if people who are experts and have both will and power to do it, why not? I'd be happy to help in any way I can, even if it includes programming (I'm not a complete noob in that area, but still a noob).