Large organizations do it for different reasons. To use their own directory service (LDAP/AD), to more easily integrate it with their other tooling, to be in co

Large organizations do it for different reasons. To use their own directory service (LDAP/AD), to more easily integrate it with their other tooling, to be in control of where their data is, to have more control over availability, to be able to add layers of security (VPN, etc.).