Nor do most other system builders. You're basically only getting some extra connectivity (if you need that much go with a workstation board and a add-in RAID card) and some larger heatsinks/heatpipes sitting over........nothing.
Having said that, the Sabertooth's 5-year warranty makes it more interesting- especially when it comes time to on sell. The board itself performance wise is good- but then, not many P67/Z68 boards aren't. What makes the Sabertooth a better proposition than most is that Asus haven't tried to go balls-out with the performance parameters -it's not specced for DDR3-2133+ (which is problematic for a lot of boards in any event), and the OC ability is middle of the pack.
What makes the boards appeal is that in some markets it is actually a cheap(ish) board -by P67 standards. Here, it retails for the same price as the Pro and the UD4 -the latter being a pretty average board- which makes the Sabertooth a good buy.
I'd agree with the MUX-120 cooler...except that it also is 160mm+ in height. Removing the side fan to accomodate it will almost certainly elevate GPU temps.