have them on all the road bikes, all have cadence. Its hard not to have some measure, even if its strictly a fitness program. Training to race, its not effective to not have one. Rode enough years, way back, without one, and training was tough when all you had was a stopwatch to gauge progress. Guessing distance and pace was always crap shoot, with numbers going however you felt that day.
Until now the MTB/commuter has been lacking one, but that changes now that the old Cateye Micro is being handed down to the MTB and a new Supergo is takin it's place on the roadie.
I even broke down and got a HRM to learn all the ugly truth...