... because Quincy starts out far from where the series ended up.
Here Quincy is the medical examiner in a number of cases that at first look like rape cases perpetrated by some kind of maniac preying on random victims. But then he sees a pattern in the murders and it leads to city hall. It's odd seeing Quincy have such a cynical take on government after watching him screech about needing government intervention in so many of the later episodes, but then you need to remember that this series premiered two years after Watergate, so cynicism towards government was at an all time high.
It looks like Lee, Quincy's girlfriend, was at first going to be some kind of regular character helping Quincy in his sleuthing, but she got dropped after four episodes. Also note that DNA evidence would render lots of these old mysteries moot such as the question - did the same person commit all of these crimes?