Why does baseball do this?

The Red Sox and Rangers took to the field Friday night to play a baseball game. Over the course of their next 9 offensive innings, the Rangers scored 6 runs. Over the course of their next 9 offensive innings, the Red Sox scored 6 runs. Tie game, right?

Wrong. That game ended in the bottom of the 6th, with Texas up 6-0. The Red Sox still had 12 outs to go, and everyone who's ever watched a game knows that a game's not over, even with a 6 run lead, with 12 outs to go. But baseball's rules decree that that game is over, it goes into the books as a complete game for Rangers starter Kameron Loe, and the team's move on. That seems silly. Everyone knows the rules, and it's been that way for a long time, but it's silly anyway. You never see an NFL game stopped in the middle of the 3rd quarter, regardless of score. The NBA would never declare a winner based on 2/3 of a game. But for some reason, baseball, in one of those "from the murky past" rules, has decided that the game's over.

Now, if the umpires had called them off the field 2 innings earlier (as they should have done - the rain was no worse in the 6th than in the 4th), then the game would have been a non-game. But since they finished playing the bottom of the 5th, it was an official game, even though they didn't actually finish it...