I was surprised that the RTV's didn't have a tach, but after owning one for a while I really don't see the need for one. I would rather have an odometer.
If the RTV's had a manual trans, a tach would be more essential.
Also with the hydro design they have and the built in braking when you let off the accelerator it's not like a manual trans that you could actually over speed the engine when going downhill.
Just my .02 though.