There's a quote often falsely attributed to John Wayne "Life is hard; it’s harder when you’re stupid". Some folks see that as good, some as bad. A classic argument of individualism vs collectivism. Obviously the individual is better off if individual stupidity is not punished and obviously the civilization is better off, especially in the long run, if stupidity is punished, so opinions on punishment usually simplify down to an argument about individualism vs collectivism.
The Vimes example is about the fact that being poor to start with is more expensive in its own right.
Vimes does not make a stupid decision not to buy the expensive boots, they are simply more than he can afford in any reasonable period.
There is another saying "making your first million is hard, making your second million is inevitable"