So we're talking about pay-per-play. This never used to be the case. You would pay a simple fee and play the game. Is the new fee necesary? Yes. It used to be that the
gamer would provide the server. With a game like Starcraft, or Tribes 2, or Quake, or Counterstrike, the gamer would either host a game or buy a dedicated server with his own money.
but now, some games don't give you the "host" option. Take Planetside, for example, a game due to release within the next four years, that is pay per play. The way it works is, the battle is 24/7, on a gi-normous planet, and you fight for one of three empires for control of as many of the 10 continents as you can grasp. The game also has realtime weather effects on the planet's surface, including a full wind system.
Anyway, enough advertising, the point here is that the company actually provides the server. They have to buy the 20 some linux mainframes, at an ubercost, and supply the monthly bandwidth for thousands of players. That will cost money, which is the same reason why internet providers require you to pay a fee. It all comes down to who is providing the bandwidth. With games like Quake, the player provides the bandwidth, so the company doesnt need to pay anything. But with a game like Planetside, where the company provides the bandwidth, they would obviously need a fee.