well, i never thought to check something like that... its like asking a car dealer if the model he is selling me comes with, or without tires. Why would anyone buy a car without tiers? (or a game without single player?).
That's a ridiculous, and invalid, comparison. A car without tires doesn't drive. A game without single player *does* drive, and quite well.
The root of video games, the oldest, were ones that essentially had no single player. Stuff like Pong, Joust, Battletanks, those were multiplayer games. The point of a *GAME*, historically, has always been to play it with other people. What you're doing is like complaining that Chess or Checkers don't have a single-player mode.
Even today, there's a *reason* that fighting games, party-style games, and multiplayer focused Shooters and RTS and TBS and Sports games dominate, because that's what gaming is, playing with other people. Single-player is something that came later.