It is more accurate to say that the point of Bitcoin is everyone has perfect information about how much money everyone has and who they transact with. The hackers are free to send the stolen money to someone else with no central authority to stop them, but an exchange is likely to reject that because they deal with fiat and therefore have to meet certain legal and ethical standards.

The hackers can still spend the money on something else provided the other party doesn't hold themselves to the same standards.