Hi there!
I live in Finland and we use metric system here. It's no fun to share your workouts via FB (or other services) if the recipients are not using Garmin Connect (don't have a profile) - when they open the workout link they see data as imperial units (miles, feet, fahrenheit..) by default. I know there's a link (in classic view, not in modern!?) from which you can switch to metric units but it's an unnecessary step - the units used could be derived from the workout user profile. I suppose in most of the cases this assumption would be correct.
br,
Anssi