Yep odd too so many posts like that. I'd hazard to say that if you feel so insecure that you think it's life threatening to have a professional set up your kit, and can't verify if it's been done properly within 20 seconds you're probably the type of diver that most needs help.
If you follow pre-dive and buddy check procedures properly you will not even enter the water, never mind submerge even if someone completely messes up your setup.
I think the generalization of "Profession" and the reasons for why someone would want to change their own gear over are a little off base.
I think by now, I can tell if someone set my gear up correctly...I just don't like to find out that someone left a little pressure on my din connection, blew the O-ring out and then put the unit back together (as an example) on a fresh tank. I've had that event happen twice in the last two years from people not used to DIN.
When on a new boat, with new people, it is pretty hard to know the actual skill level of everyone involved..