You want unattended servers? Fine. You want someone not to be able to steal the keys from a backup? We can do that too. You want the servers to be able to restart at 2 am without getting someone out of bed to come type a passphrase into a console on each server?

HSMs were quite expensive. People made any number of attempts to make them cheap and found out why they aren't (Ari Shamir has entered the chat), often a Too Good to be True scenario.