Because it's weak. As far as I'm concerned, every player can run, jump, and shoot.
How can you leave out such big parts of players game out of a comparison?
Athleticism and Build mean everything when a player utilizes them as effectively as Jordan did. His whole game for the early part of his career was based upon his athleticism, not his shooting ability. Sure, he had a nice shot, but it can't be compared to his shot in the latter stages of his career.
You have to be more specific with examples of how Jordan's athletic build gave him an advantage that Kobe doesn't have. It's not enough to say "well Jordan had huge hands."
Players don't make excuses for how their built. If Larry Bird didn't play as well as Magic he didn't say it was because Magic had more physical abilities.
It's a whiny type of argument. If you compared who was better between players and included their physical attributes the upper hand would go to whoever you thought was blessed with less every time.
At the end of the day performance is what's important. That should be the focus.