Don't need it, but I want it. Gives me a good idea of where an engine begins developing power, and the useful rpm range (without flogging the crap out of a bike to hit the rev limiter.) Example - going from riding twins for the past 25 years, I find that the recently-acquired Honda CB1100 develops great torque and hp at relatively low rpm. And for some reason, when I think I'm over-revving the IL4 engine, I look at the tach to find I've got a long way to go, rpm wise. Unlike many in-line Japanese fours, this engine has been designed and tuned to make max power down low. The redline is at 8500rpm. Maybe my ears are playing tricks since most of my auditory experience on revving engines has been on either flat or 90 degree v twins. I like having a tach.