Wallets for storing USD are not only PayPal, there are also many others such as PefectMoney, Payoneer, Payer, Airtm etc., besides, we can also receive USD sent by people from anywhere directly to our bank account and the bank will convert it into local money.Most people don't use USD because they don't have a wallet that supports it. PayPal only works for some countries for example. While crypto wallets are almost available worldwide. That is why most people these days trade with Bitcoin and not USD.