Vaults are useful to prevent your hot (or luke warm) coins from being stolen. They give you a button to send money to cold storage.

Using them toto protect your cold storage is trickier, because then where do you send the coins? What if you fallback cold storage actually has worse security?

There are more subtle ways in which you can use vaults as a dead man switch, which current requires moving your UTXO's on a regular interval.