Because in the view of apple, manual labour doesn't count for anything "specific" even if it is a bigger, longer and more intense workout than something you would likely get at a gym. Which is right back where we started. If the watch can do it all automagically there isn't any need for 'sports specific' tracking, right? Imagine being a furniture removalist and how you can set your watch to get whatever you get from setting it for your gym session?
And yes, you're probably aware and it also kinda beside the point, game-ifying manual labour is a thing many people do but also, seemingly, not using an apple watch to do it.