Good and Evil are human concepts, but their lines are often blurred. What if the lie was for a good cause? To prevent hurt feelings or protect another? Is that bad? Could some supernatural karmic force tell the difference between evil and evil for a good cause? Doubt it. It's not so much as people get rewarded for doing good. They get rewarded for making intelligent decisions. Most of the time, a good decision is also an intelligent one. The reward? Not having to take two steps back because a bad decision made them pay big time. I'll use lying as an example again. Building lie after lie isn't very smart; eventually someone is going to pull out a block from that Jenga tower and the whole thing is going to collapse.
Would it be nice to be rewarded for our good actions? Of course. And many people do. But not because of Karma in the ideal sense. Someone could just as easily have done bad deeds their entire life and never have a single misfortune befall them. What is good or bad to us is different to other people; good and bad are constantly shifting. An intelligent decision stays constant, and has a more predictable outcome.