The other day I passed by the pharmacy in my local Safeway. (The Safeway is the second store on the site--the original shopping center was too arty for commercial tastes, because it didn't open up to the road, so about 15-20 years ago so it got redeveloped into a more "traditional" strip-mall format with a much bigger Safeway. But the pharmacy was an issue, because there's also a drug stair in the center, which obviously didn't want the competition from a supermarket pharmacy. Resolving it delayed the redevelopment for a good while.)
Why have a pharmacy in a supermarket? Come to think of it, why have a bakery, a delicatessen, and a bank in the supermarket? Why have a meat counter and a fish counter? After all, in many European countries you have (or had) separate butcher shops and patisseries, etc.
The answer, in my mind, augurs ill for any idea of vastly expanding farmers markets. Americans, mostly, seem to have voted for convenience, for saving time, and we see the results of that election in the design of our supermarkets. I'd guess that going to any farmers market is going to cost the consumer 40 minutes of driving time and shopping time. Add that to higher prices and it's going to limit your sales potential, even if the produce is healthier and tastier.