NPCs are fine and should be allowed as long as they do not tilt the balance of Roleplay toward one of the sides. For example heading to the Pershing Square bar, since it's a State one you can RP a bartender who servers the people. Or you head down to East LS Carwash and RP some kid washing your vehicle while you and your mates are in it.
NPC Doctors and K9 units etc. do tilt the RP to the Law Enforcement's side. Which is an aspect of powergaming and should not be allowed.