What if you want to use limit break while spineshatter dive is on cooldown? You will just stand there 3s doing nothing. Maybe the target will not be in melee range anymore.
What if you use the macro the moment you get stunned, it will run anyway but it will skip 1 or 2 lines.

There are only 9 skills + 2 additional + limitbreak, why macros? In PvP every second counts and you don't want to limitbreak a 100% target.
The only macro that would be okay are targeting macro.