On the commercial side, it's the curse of the pareto principle and the "good enough" approach that is the rational consequence of money-maximizing strategies.
For volunteer/free software/etc. it's both people being used to working in commercial settings on the one hand, and being ok with scratching one's own itches first and foremost on the other.
Prisoners? No. Influenced to varying degrees by everything we have experienced, including, obviously, our upbringing? Certainly.