Ford and Honda seem to be the ones using thinner oils like a 5W20, and although primarily in the US they seem to have started using it in some other regions. They're also companies that don't seem to have many turbos in their line, at least in the US. If either do offer turbos what kind of oil do they use ?
Looking at something like a Honda Civic, which is a common car to be modified in the US, when someone puts something like a turbo on one do they typically continue to use 5W20 ? Some state that the engines are designed to be used with 5W20 (although special ones must be built or selected for the US market as both companies seem to use heaver oils overseas), so does one continue to use a thinner oil with a higher output engine that will tend to be driven harder ? I'll guess not, unless someone is willing to sacrifice engine life for maximum power output.
Generalizations help to navigate thru some of the ideology:
Most engines that use turbos seem to use heavier oils.
Some of the highest rpm produstion engines available are on sport bikes, and they seem to use heavier oils.
Turbodiesels use heavier oils, as typically high torque and long life are expected.
Most countries outside of the US seem to use heavier oils, including companies that use thinner oils in the US.
Thinner oils are being used primarily for either maximum power output where long engine life isn't required (thin oils aren't typically used for endurance racing), for increased fuel mileage, or for colder weather.