DC fast chargers primarily benefit people who are traveling
through an area - not for people who live
in the area (those people can generally charge at home for local travel). DC fast chargers tend to be strategically located in areas through which people typically pass while traveling from and to other locations.
Take Tyler, Texas, for example - an East Texas city with a population of about 110,000 where there are no Superchargers (or
any fast chargers as far as I know). There's a Tesla service center there off of a loop around the city, but the vast majority of that traffic is local. Interstate 20 passes through Tyler, but stopping at the service center would require an extra 30-45 minutes of driving. There are Superchargers in a
much smaller town of Lindale 15 miles down the road. These chargers are located right off the Interstate and benefit those traveling between Dallas and Shreveport.
The best place for Superchargers isn't always whereTesla service centers or galleries are located. It can cost well over a million dollars to install a bank of Superchargers and that's more than the value of many service centers themselves.