Because there's no bankruptcy filing, no address of their offices, no known whereabouts of its founders and executives, no way of knowing if they stole customer funds or simply gambled them away, and no one knows who has the legal jurisdiction to investigate them.

They're simply trying to disappear slowly.

When will they learn

Only reason to have coins in a cex is when converting to fiat, even then you might be better off using a dex and moving in and out of a USD stable coin for day trading and fiat conversion.