I think it's a rather a budget and rating issue. Staging good fight scenes takes a lot of time and money. Staging realistic knife fights is going to be a mess that would never be allowed to air.
That's a good point; really, many forms of personal combat could potentially get QUITE a bit more bloody and disturbing than we ever see from the majority of TV shows. I don't mind them skipping out on all of THAT. There are war dramas and such that will actually make more of an attempt to really show that kind of realism, but outside of that kind of production, where showing the true results of such violence is part of the point, I don't think it's necessary or desirable.
Stopping short of that, I've always pegged the lousy Trek fights to, as you say, a lack of resources. Trek's budget has always been fairly limited, and while I would have loved to see fights that were more thoughtfully choreographed and faster paced, but the reality of the production just didn't allow for it.
They also don't wear any sort of protection against blades and disruptors, going against Klingons twice their size in metal body armor.
True, but I don't think this matters, honestly. I see people point this out often, and it bugs me because nothing the Klingons are wearing does anything either. Nothing that ANYONE wears - Klingon, Cardassian, Jem'Hadar - in combat seems to have any effect whatsoever against either fist, blade, or energy weapon. So it's kind of moot, and the metal-looking bits adorning Klingon uniforms are apparently purely ceremonial.
Don't misunderstand: I'm not defending this fact as logical. The fact that Klingon "armor", despite it's appearance, apparently does nothing, is itself kind of silly. So I'm not trying to say that it's perfectly ok that no race in the galaxy seems to employ any kind of body armor, I'm just saying it's not fair to single out Starfleet.