Weird Chess Rule Number 1 - you HAVE to make a move
This is a fundamental rule of chess and in quite contrast to real war/battle like situations. In a real battle, you may not want to make a move if you're sure that the move will cause you harm. You may choose to keep your soldiers in the exact same position and wait for the enemy to move and then react accordingly. Unfortunately, in chess, you cannot do that. You cannot say "pass" and give up your turn.
Consider this position -
[FEN "8/8/8/8/8/K7/B7/k7 b - - 0 1"]
[Event "Black to move cannot avoid putting the king in check"]
Here, it is Black to move. The Black king can technically go to g8, g7, or h7. But if it moves to either of these squares, it will walk into a check and thus be threatened with capture. So what should the outcome of this game be? We aren't allowing Black the option of not making a move and at the same time forcing Black to make a move that would move the king into check, when in fact the king is quite safe in the corner and White has no way of winning.
Thus, to be fair to Black, this position has to be declared a draw.
Unfortunately, this is not true for every position where Black (or White for that matter) has no moves that do not lead to putting the king in check.
So, in this position -
[FEN "8/8/8/8/8/K7/2Q5/k7 b - - 0 1"]
[Event "Black to move cannot avoid putting the king in check"]
Black has no moves, but that doesn't mean the fair thing to do is declare this position a draw. However, that's unfortunately the current rule in chess. It's no wonder that the stalemate rule has varied greatly throughout history. At the most, one could argue that it's not fair to ask Black to move the king into a position where it could be attacked, but since we insist on weird chess rule number 1, then the fair thing to do is to declare this position a draw.
There are also stalemates that can occur because the side is forced to capture its own pieces in order to make a move.
Changing the Stalemate Rules will Greatly Change Chess Endgame Theory
This is another reason why the flawed stalemate rule is allowed to exist. We have studied chess endgames with this rule in much detail. Changing the stalemate rule will significantly alter how we understand the game of chess and much of our acquired knowledge of chess will be useless and even misleading. For example, consider the simple case of king and pawn endgames. If stalemate is not a draw, endgames like these will have to be declared to be winning for the side with the extra pawn.
[FEN "7k/8/8/8/8/8/6KP/8 w - - 0 1"]
[Event "White wins if stalemate is not a draw"]
1. h4 Kh7 2. Kg3 Kh6 3. Kg4 Kh7 4. h5 Kh6 5. Kh4 Kh7 6. Kg5 Kg7 7. h6+ Kh7 8.
Kh5 Kh8 9. Kg6 Kg8 10. h7+ Kh8 11. Kh6
Fundamental endgame positions like these will have to be re-evaluated and in turn those endgame studies which rely on these fundamental positions will have to be re-evaluated. In turn, our understanding of the middlegame will also have to be altered to fit this new endgame knowledge. Thus, it's very impractical at this point in history to change the stalemate rule.
Conclusion
We have decided not to change weird chess rule number 1. Stalemate is a by-product of that rule. It's not fair to force a side to move its king into check, thus, in this context, it makes sense to declare stalemate to be a draw.