IMO taping wirenuts is a hold-over from the old Knob & Tube days when all splices were twisted, soldered and taped. The old-timers would tell the young pups they had to tape to do a good job. Us young pups became the old-timers, and the idea is still there. Wirenuts today will do the job just as fine, with or without tape. If you're worried about vibration, dirt, or something, go ahead and tape for your peace of mind. But maybe, your enclosure or termination device is not really appropriate for the purpose or conditions of use. Maybe????
