- It's currently easy enough to hack the same money. Way less effort.
- Doing something physical puts the crime into areas where law enforcement is used to working, used to catching people, and leaves physical evidence in the world. At least in the developed world, kidnapping rich people goes to the head of the line for police resources.
- Most large projects use multisigs. This means you may need to kidnap a half dozen people in multiple counties. Doable, but the odds of none of these failing and exposing the whole operation goes way up.