This is a great point, especially for multiplayer games. There always has to be some sort of negative loop for the winning side so that the more this side wait to take advantage of their position, the more they start to lose the position. Not only does this presents an interesting strategical time constraint but it also gives a chance for the losing player to come back and win the game, resulting in that a player never really feels that the game is over and he is just waiting to lose.
One amazing game in this aspect is Starcraft 2. Lets say that you and your opponent get to 100 supply (army size, roughly, for those who don't know the game). Then you both enter a battle and you lose - now your opponent is 80 supply and you are 40 supply. Pretty scary, right? What happens next is that often the winning opponent will retreat and defend (a tactic the commentators call "when ahead, get more ahead") but if he waits too long it's possible that you both will have the time to gain another 100 supply. Now.. 140 supply (you) versus 180 supply (him), is not so scary anymore, right? You went from being half his supply (50%) to now being almost even (140 is almost 80% of 180). These numbers are not perfect but they illustrate how the game works, roughly.
This also is very interesting because it puts the winning side on a dilemma. After losing the battle the losing side will almost always have to retreat and defend but the winning side has to decide - do I attack now than I have the advantage or do I retreat as well and "get more ahead"? For people watching the game it's easy to look at numbers for both sides and know what is the right choice but for a player inside the game, who has no information about the other player's army, it's a very tough call to make. What if the other player has a hidden defense army back at home, or just a few strong units there? Should he risk attacking now and possibly lose the game if he is wrong? If he goes back, how long does he have to grow stronger before his opponent catches up with him and his advantage is negated? This is not only something that applies to Starcraft but any game with a proper negative feedback loop.
On the other side of the equation are games like Heroes of Newerth, which I've been playing a lot recently. It's a pretty good game but there is no negative feedback loop. Once your team gets a few kills on the opponent team, it will grow stronger, and as it get stronger it will get even more kills - creating a positive feedback loop for the winning team. Once the winning team is strong enough to start destroying buildings of the losing team they will grow even stronger and the other team even weaker. HoN games can last up to an hour and a half and no one wants to spend all this time just waiting to lose as you see your opponents get stronger and stronger, so people will always type "cc15" after a few deaths, even if the game is just beginning! "cc15" means that you should give up the game when it reaches 15 minutes, which is when the button to give up is enabled. It is still possible to win a losing game because HoN is pretty cool but I've always thought it had this huge fault in it's design and the fact that people want to give up the entire game when it's not even 10 minutes in shows that...