It would not bother me personally unless my appointment time were lengthened 10-15 minutes at the end, so our total time wasn't cut short. If it was cut short and my bill were not prorated it would bother me. Admittedly I have some trouble with punctuality in general so I think that's why it would not bother me.

At the end of the day, however, it IS unprofessional and I can understand why someone would terminate soley on those grounds.