You may want to re-read your comment. If Toll-free inbound is higher than outbound, then why wouldn't they do outbound more often? We're talking about (in many cases) businesses like banks which offer toll free numbers. So obviously cost is not the dominating factor here.
Some systems did implement outbound calling for increased security. I'm thinking dial-up (BBS/remote access) scenarios. Windows NT, for instance, allowed you to allow a user-defined or preset callback number. Although, for user-defined, its more likely a cost issue than security.
Some systems did implement outbound calling for increased security. I'm thinking dial-up (BBS/remote access) scenarios. Windows NT, for instance, allowed you to allow a user-defined or preset callback number. Although, for user-defined, its more likely a cost issue than security.