In my experience west coast flights (esp. Compass) consistently have beverage service and as you move east, it seems that the number of excuses for not doing beverage service increases, especially on short hops ORD-, JFK-, DFW-, DCA-. Just my limited experience though, but I flew SAN-LAX a lot of times this year, which is a ~100 miles market... I seem to recall beverage service most of the time. Also it seems like SkyWest, Republic, PSA and Envoy have significantly worse FAs than Compass. Again, based on my experience...
(Just got off a SkyWest flight where the FA wouldn't stop yapping about connections for 10 minutes, and kept announcing we were 20 minutes early every few minutes --- At least there was full beverage service though -- YYZ-ORD, so I guess that makes it ~400 miles.)