Not at all. UPS does it to become more efficient, and that works because UPS has a lot of stops to make. But GP's grandmother did it to be safer even though it was usually less efficient.

They make lefts, but they do routing in advance and heavily prioritize routing using right turns. There is no hard and fast "zero left turns" routing policy or driver policy.

Not really the same thing. UPS is optimizing the efficiency of a multi-stop route given that making a lot of unprotected left hand turns (especially with a truck) can add a fair bit of time to a route.