I remove reflectors for three reasons:
- I often run my bikes on a bike stand (pedaling to tune drivetrains, etc.). Reflectors add weight to one part of the tire/wheel assembly, and high spinning speed will cause the bike to jump around while on the stand.
- Since reflectors add weight to one part of the tire/wheel assembly, with such a bias to one spot, it can make tuning your wheel bearings difficult, because the wheel can never be left to very slowly spin in a neutral environment.
- Reflectors make wheel truing more difficult, as they often conflict with a spoke wrench.
Some or all of that may not apply to many people, but tuning and adjusting bikes is great therapy for me, and these are the reasons I remove wheel reflectors from my bikes.