The Nostromo crew is not all blue collars. Obviously, there's a Captain, second officer in command, flight officer, science officer, etc...I would only say that Yaphet and Harry D. could wear the "blue collar" label more easily than the others. Ash is Hal from "2001 A Space Odyssey": clear mission and mandate, works hand in hand with "Muther" the main computer on board.
The mission and its success is simple: get to the surface, explore/investigate and come back with something, no matter what (human crew expendable). That's why Ash didn't respect the orders given to him by second officer Ripley(while Dallas, as Captain, should've known better than to ask to open the doors with a unknown "thing" attached to the face of one of his crew member:behave:rolleyes)
Ash is evasive with his knowledge/research of the Alien. He knows more than the crew will know and it shows throughout the movie (keeping the crew from killing the Alien after it emerges from Kane's body is one and his "detector" is no better at detecting clearly the creature while in the air ducts of the ship).
As for returning for the cat, in real life the cat is also expendable (go to the store and buy another one:facepalm).
Are we sure that Ripley was discovered by "sheer luck"? If I was Weyland-Yutani Corp, I would be pissed if my tug and its mining load had not arrived to port after...30 years!!
They send a search party (Marines, no less) toward the last position of the ship...and yes, it took them that long (they were,after all, far from our system when they were woken up by Muther).
Yeah Parker and Brett are blue collar but the flight crew I would call journeymen, competent and skilled just a bit burn out and unmotivated.