To add to this: while the PCs, typically, do not want to be in combat, I assume that people playing a game which has an intricate combat system enjoy that system. And so the reason for having combats as part of the game is that pleasure.
Part of the pleasure consists, as you say, in successfully deploying options. But this doesn't have to mean optimally deploying options. There doesn't need to be some unique optimal play in order for players to enjoy making game play decisions. There just has to be an interesting context for decision-making. Varied encounter set-ups, and synergies between the various players' options, are two ways to create this sort of interesting context.
As far as consequences go, these can be significant without involving any fatality. The same "narrative consequences" that various posters are suggesting will drive players not to rest, can be used to create consequences for fights other than death.
