[aschen]

thermodynamics and basic mechanics suck in US units. When I was in school I did all my non symbolic work in metric and then converted back to metric in the end. It was too easy to miss points by being off by 32.2.

The golden engineering rule of "always carry your units through" breaks down in some instances for SI.

Many places use mixed unit systems as customary.

The reason why we don't switch is a good lesson in what drives adoption in my opinion: need and not just convenience. It would be a giant PITA for alot of industries and the upside is only slightly less annoyed technical staff. People dont care that much about annoying others slightly less.