I don't agree that severe turbulence is that easy to avoid, and I particularly don't agree with that in regard to moderate turbulence. In many cases, moderate turbulence is just a fact of life.
In my experience, there are three types of severe turbulence:
1) Convective activity (thunderstorms). Yes, this one is pretty easy to avoid, at least most of the time, given modern technology. It's also the most dangerous, so it's good that it's reasonably avoidable.
2) Clear air turbulence at high altitude related to the jet stream, and shear. As a friend of mine used to say, "stay away from the elbow in the jet." However, it's not always there, and it's not always that bad. But sometimes it is. And the jet stream covers a big area, so sometimes you can't get to where you are going without flying through some of those areas.
3) High winds and mountainous terrain. Sometimes if you are going to mountainous areas, you are just going to get rocked around.
In desert areas, moderate turbulence is common. Often going into the Palm Springs area, you will get moderate turbulence. If you don't fly through it, you won't get there. Same thing with cold fronts on the west coast. It is just a fact of life. I flew an ILS the other day that seemed like I was on the inside of a washing machine.