I can't even begin to count the number of people who run from my No-Dachi. :) But they eventually get tired and it catches up. :)
Honestly, I think it is partly the thought of the damage hitting anywhere. Take the aforementioned No-Dachi, it has a sword, which isn't the best melee weapon, but on a NDA, it does 16 points of damage with TSM active, with a -2 modifier. Most mechs don't want to take a 16 point hit to one location. Yes, it could punch for 2x14 damage, and on the punch table too, but psychologically the sword is scary because of the -2.
So if I have a 4 pilot (you better believe I upgrade the pilot), and have TSM active, I can run 9 hexes to you and take a swipe without paying for my run. Or if I feel like it, a 28 point kick (that tends to take legs off).
For the Hatchetman, that is 9 points of damage with a -1 to hit. Nothing to sneeze at, especially if it can get behind you.