The hive must be pretty clean

They mentioned the heat, but it was dry heat. I would think it smell pretty rotten but most movies don't seem to mention smells.

Guess not.

Dallas reacted to acid fumes when the hugger bled on the Nostromo, and Ford reacted to the smell just before the Engineers head exploded, but nothing really beyond that.

Guess Alien hives mask that kind of thing.

The dead bodies on the Auriga may not have started smelling yet, explaining the lack of reaction from the Betty crew.

The Marines could be real life well Alien Franchise Bear Grills who had been in some bad situations of survival and so maybe nothing like that offends them...

Once you have chowed on some Space Grubs for a time, maybe the smell goes away ;)