The most money I have ever had on my PayPal account was 100 bucks from a reversed transaction (like, double booking of a hotel room or wrong item sent), otherwise it's just a gateway. It would be annoying if my PayPal account was locked, because I use it a lot to order pizza online and a few small purchases. I could just use my credit card or something else but it's more clicks. And I know a lot of people who do it like this. The only thing lost is convenience. No past purchases, no digital identities.
Maybe you meant the merchants who really amass thousands but I suppose they are a small minority of active users.