Because the U.S. financial system, and access to it is a very powerful tool in terms of international diplomacy, and a crucial source of evidence/intelligence f

Because the U.S. financial system, and access to it is a very powerful tool in terms of international diplomacy, and a crucial source of evidence/intelligence for law enforcement. Trivial abilities to move money around and an inability to lock out financial endpoints would completely neuter it's utility as sanctioning measure.