"Seat open" pet peeve

Don't know if this bugs anyone else or if anybody's even noticed, but whenever I see a seat open up on a table I'm at and there's a waiting list, there's usually about 1 or 2 players at the table who get all bent out of shape if the seat isn't filled within a couple of minutes. They'll say to the dealer in a nasty tone "Hey you know we've got a seat open?" or even bitch to the floor person that the seat hasn't been filled. Meanwhile, 90% of the time the dealer is perfectly aware of it and has either already called "seat open" or is waiting for a floor person to get within earshot so he can notify them.

I swear, what's the big f'ing deal if a seat if empty for a few minutes. I don't see these people bitching when a player takes a 20 minute piss/smoke break. I just find it annoying as hell. Let the f'ing dealer do his job and keep your mouth shut. I swear, I've seen players sit at the table and play cards for 2 hours without speaking a word, but as soon as that seat opens up and isn't magically filled right away, they're cussing and pissing and moaning with the best of them.

Just a weird phenomenom that I've noticed. If anybody here is the kind that does this, please explain to me why, and do you honestly think that if you didn't say anything, the seat would never get filled? I've noticed it the most at Foxwoods, but that's an east coast crowd so you gotta expect some rudeness.