Encryption is good until someone leaks the private key. Depending on the application, it may be very difficult to reassign all primary keys and foreign keys whe

Encryption is good until someone leaks the private key. Depending on the application, it may be very difficult to reassign all primary keys and foreign keys when that happens, especially if they have already been used as canonical identifiers. You don't have such issues with randomly generated ids, unless someone obtains a full dump of your database (in which case you will have to think about bigger problems anyway).