Its not just the fact that its out of a can, its how its used the preparation. And TYPICALLY, if someone

's something, they do not do prep thats even half assed.
They don't remove all the frame components (chain guides, nuts, bolts, seat latches, etc) They dont adequately degrease/clean the frame, and they dont adequate remove the old finish.
QUICK=not good!
A

pain job CAN be done right, absolutely, but its got to be prepped right.
Same as $300 a gallon automotive paint being sprayed from a HVLP paint gun. PREP, PREP, PREP! I've seen so much stuff on here that is painted right over wires, grease, dirt, frame components, its just really ,really dis-tasteful. And that sort of behavior is why, in general,

paint jobs have a bad stigma.