I know this was in America, but unmarked units over here in Western Australia rarely have more than two light sticks. One on the front dash and one on the rear. Sometimes they only have the front mount and sometimes not at all, just the LED you manually put on the roof (although only detectives use that).
Pretty much what Sam said. Most people aren't familiar with law enforcement equipment whatsoever, it may not seem so but it's a rather niche interest. While I may be able to name what the police car is, what lightbar it's rocking, someone like my mother just sees a police car and nothing more.