Jem'Hadar, I think the point is was to get a more epic rather than realistic aspect to the games. In the movies, the Enterprise always suffer a lot of damage without blowing up, while ennemy ships tend to blow after one successful hit. It goes the same for brawls in movies : one bullet or one punch is enough to deck most unnamed guards (while the superboss takes much more time), but the hero on the other hand suffer at worst flesh wounds or a bruised eye.
And most game rules usually don't allow this sort of things, except with incredibly lucky rolls, something which doesn't happen every time.
"The main difference between Trekkies and Manchester United fans is that Trekkies never trashed a train carriage. So why are the Trekkies the social outcasts?"
Terry Pratchett