In some ways they are for consumer products. There is some percentage of people that won’t buy at all without the option. Then a much bigger percent that will still buy but prefer to use PayPal if you give the option.
In fairness, I still wouldn't call that a monopoly, just a popular choice.
I mean, I know some people who won't drink soft drinks unless it's specifically Coca-Cola and know a lot of people who'll pick Coke as their first choice but they clearly don't a monopoly on cola drinks.
I mean, I know some people who won't drink soft drinks unless it's specifically Coca-Cola and know a lot of people who'll pick Coke as their first choice but they clearly don't a monopoly on cola drinks.