More than 90% of the pay phes sold in the stores of the four major operators in the United States are iPhes or Samsung phes.
Apple and Samsung together sold 94% of the phes in Veriz stores, 95% in AT stores; T, 94% in Sprint stores and 91% in T-Mobile stores, according to the report. The most popular phe of the four operators in December was the iPhe 11, according to the firm. The best-selling Samsung phe was the Galaxy S10.
I would say it is probably because the price of most iPhes and Samsung is high enough to allow stores to profit from it.