CVS, Walmart, and Walgreens are all scaling back or shuttering retail health clinics. Walgreens’ VillageMD recorded a $6 billion loss, an example of just how difficult it has become to generate profits from a health-care model that retailers over the past decade bet would be a big win. CVS remains the largest operator of in-store clinics, with 63% market share, according to Definitive Healthcare’s annual report.