People are just lazy

I don’t run outside because I don’t like being watched when I exercise. Treadmills or gyms I’m fine with

sometimes the person could live in a dangerous area where it is not safe to run outside.

Maybe he’s self conscious.

Maybe its f***ing winter and he doesn't want to run through a foot or more of snow.

Sure, let me just go out and run on the snow/ice. Thanks OP.