Maybe because they could still refuse to pay? Anecdotally, I know of at least two pizza shops near me that only accept cash, and don't deliver. They're not hurt

Maybe because they could still refuse to pay? Anecdotally, I know of at least two pizza shops near me that only accept cash, and don't deliver. They're not hurting for business in any way. They're also on their 3rd and 4th generation of owners, so maybe they never adopted the practice of accepting credit cards.