When I used to play 5-player five hundred, only one of the five players could win. That didn't mean there were no win conditions. Nor did it mean that the game was fun only if I won. I've also played MtG with many players (6? 8?) at the table, and probably never won (I'm not a particularly good MtG player) but there were win conditions, and it was fun.
But as
@chaochou has posted, games like five hundred and MtG are structured around win conditions, and playing to win. Combat in D&D is much the same in this respect.