I was thinking about a scenario like this earlier this year.

Most users alone don't have enough to exceed the exchange's USD or crypto reserves. But if a user finds an inflation bug in a shitcoin traded on that exchange, the exchange must halt withdrawals when that inflation bug is found and exploited. Or they lose significant USD/crypto reserves and probably go bankrupt.

This incident proves that my theory was too narrowly focused on inflation bugs in shitcoins. Rather, ordinary security vulnerabilities can be leveraged by hackers to trigger a halting of withdrawals. Many programmers, but especially shitcoiners, are lax with security, so we should expect these sort of hacks to continue indefinitely.

For exchanges, this provides some disincentive to trade shitcoins. But they likely haven't even tried to guess how big the risk is to them.