The perk is the cheap ticket you are travelling on.
No, I don't get any perks where I work. I get club over four hours, economy otherwise. I'm often upgraded (about 1 in 3) on the short haul flights, and thus all things being equal fly with the airline that provides my frequent flyer card. If you routinely upgrade staff before me, I don't get upgraded and have no incentive to fly with you.
And yes, passengers do notice, because invariably the crew look after their mates first, or even worse spend most of the flight chatting to them, and the service detiorates for the paying punter. Doesn't happen? I can give you an example from BMI.............