PayPal just happens to be one of the most used online payment providers, being very trigger happy on this one due to pressure from regulators. This makes PayPal unideal for any businesses that deal with digital goods.
Payment processors will ALL (including stripe, authorize, adyen, etc) lock your account (with your money still in it!) if:
1) You're taking money for a product that will be delivered in the distant future (like tickets for an event, or preorders)
2) Your account has a sudden change in ticket size or quantity
3) You're violating their TOS. On HN that might look like a service that winks about piracy, or being a spamming tool.
Ever since I learned about this ~10 years ago, I've been looking into the details every time someone gets their account shut down, and it's always the above. The way people describe what happened to them to carefully leave out one of those points prevents it from ever being shocking.