More specifically, it excludes the night club district which is when the 10pm to 5am service time would actually be in demand.
I'm in the beta but still haven't tried it because unless you live directly in the zone it operates it's not useful. Even then rarely am I ubering in the middle of the night anyway.
As is, I'd have to take an uber to the zone it operates in after 10pm, then get a cruise point to point in an area where everything is closed, then take an uber home.