Why do people do good ?

I always have this nagging thinking...
why people do good ? or at least...don't do bad things...?
why people choose a life where they have to work hard to earn their livings while there are other much easier and profitable job out there ? presumably illegal of course...
come on...think about it...you work nine to five for, let's say, 10 years...and I don't think they money earned wil be as much as if you, say, rob a bank...
so why most people choose the nine to five life rather than the rob-a-bank life ?of course some people do choose the rob-a-bank life...but that's beside the point...
why there are relatively more not-bad people...I won't say good, but at least not bad...in this world ?
I can think of a few explanations...
first...
if all people think like I do and decided that the rob-a-bank life is more profitable...then which bank that they are going to rob ? since everyone has gone bad, which not-bad people will run the bank ?
in the end the bad will rob from the bad and vice versa...
so some people must stay not-bad...who ? we don't know...
second...
people still believe in God...or at least a higher power...
they fear of the punishment that may come if they do bad things...they fear the retribution...hell...or trapped in endless cycle of suffering...
so they live life carefully by not doing not-bad things...not sure about good things though...
thirdly...
there something called moral...
even if someone do not believe in higher power or being...he might still have moral...
moral...man's capability to discern right and wrong...
so even though he may not like the life that he lead...but he knows that the alternative is morally wrong...
unfortunately, moral values are determined by the society and it is degrading...
so maybe in the future, stealing is morally correct...I don't know...
Plato will be disapointed to see his universal law of morallity doesn't apply there...ha..ha..

so will the future be bleak ?