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