Being on the outside looking in I suppose I only have a limited view of this. I would love to switch from an office job to flying, and personally I would not mind doing the menial work if it came as part of a flying job (well, I need the exercise anyway). I can understand you are not going to be doing it all from the start and perhaps they do need to extract a bit more value from you if are not experienced enough yet to do the higher value jobs. If you are paid for it then why shouldn't you roll up your sleeves and do your part.
What I don't like the idea of is what I see in say Ice Pilots, where it seems like the "promise" of flying is held as a carrot to extract some cheap labour. Come along, break your back doing loading/cleaning and if you hang around for a year or two and put up with their crap, perhaps one day, if someone else does not pinch it, you can get a chance to fly, maybe, as long as you don't piss off the boss. It seems to me to be on the same level as pay to fly or fly for free - using someone's passion and dreams to cheapen your operations. Its not about doing the non-flying work, its that in being hired as a pilot (after training and hour building etc) should have a reasonable expectation to exercise your skills, not just have them as a flag that you are keen to do anything near an aircraft.