Nurses in short supply are recruited by agencies. They lure them away with money. My wife is a charge nurse, and she sees nurse leave, and come back, because the working conditions at her hospital are better than the others, even though they pay less. My PD nurse says her division makes the hospital money, and the hemo patients do not. With the coming medical cutbacks, I think they're going to make "incentives" for hemo patients to go PD.
Having checkups in the clinic is probably for convenience. I know that our neph goes to other clinics - I don't know how many - so it could be a volume thing. For us, having the checkup at the clinic is a nice "one stop shopping" experience: talk to the neph, get epo shot, get supplies that the warehouse no longer handles, and ask questions of the nutritionist, social worker and anyone else there.