thieves: it's fine, you can ring them and explain the situation as we remove your fingernails

(This technique has been used in real bank robberies; both of the people required to open Northern Bank had their families taken hostage https://www.theguardian.com/uk/2008/oct/09/northernbankrobbe... , and that was for a mere £28m in easily traceable physical money!)

Actual thieves: "Cool. We're going to kidnap you and beat you until your other signatory coughs up access."

Many people are very rich and don't own crypto. You can kidnap them also and do the same thing. This is common in many parts of the world. The US used to have this problem also and got it under control by the state focusing on capturing kidnappers and putting them in jail. Crypto does make the transfer of anonymous money a bit easier, but so does motor vehicles.

+1

Something something xkcd $5 wrench