The early self encrypting drives did not do a great job on key management. The eDrive spec adressed the level of detail and care that is needed to properly handshake with a machine during boot and avoid leaking keys. Not all controllers updated to support eDrive, so the encryption in the controllers ends up being ignored in enterprises.
It is also important to think through the infrastructure for managing the keys. Is there a good way to back up your key? If your machine dies, can you move the drive and unlock it on another machine? Can enterprise machines be centrally managed?
Like any problem in the security world, meticulous care for fit and finish is necessary before it really becomes useful. So far, only a fraction of SSDs go that last mile.