>>513075474 (OP)
It's not because they are incapable, they do it intentionally as part of their cultural mindset. Basically, ideas like fairness, honor, etc are things that only matter to White people. For non-Whites, they see everything through a lens of assuming that someone is always getting scammed or cheated or mistreated somehow. If they don't feel like they are scamming you or cheating you in some way, to their way of thinking, that means they are getting scammed and cheated.
Say you hire a White plumber to fix your toilet or whatever. You will discuss things like price, expected results, how long it is going to take etc and come to an agreement. And then ideally the plumber does the work as expected and you pay him what you agreed to pay him and both parties will walk away satisfied.
But put a shitskin in this same situation, and he won't be satisfied. To him, you being fine with the outcome means that you must have cheated him in some way. The shitskin will ALWAYS do something to try to fuck you over so you don't get exactly what you expected to get.
He will either do the work and then start demanding more money than you initially agreed to pay him. Or he will intentionally do shoddy work, lower quality than what you expected for the amount you agreed to pay him. Or he will simply make a mess and track a bunch of mud and dirt in the house, trash everywhere, etc. Just to make sure that he fucked you over just enough to make him feel like he won the cheating contest.
This attitude is nearly universal among them.