Historically, it was to avoid installing and putting a server certificate on a radius server, or if you have an LDAP server, you would avoid installing a radius server period. There are two ways you could do this:
1 - Setup a radius server with no server certificate. Setup a controller with a server certificate, enable termination and have the controller point to another radius server for authentication*. The drawback is that with Microsoft Windows Radius servers, you could not do machine authentication with this setup.
2 - Setup an LDAP server. Setup a controller with a server certificate, enable termination and have the controller point to the LDAP server for authentication**. The only problem with this setup is that you would have to install custom supplicants on all of your windows endpoints, because they do not support EAP-GTC, so you would end up installing software on all of your endpoints.
These days, everyone has gotten used to installing a radius server, whether it is the built-in Microsoft One or ClearPass, Cisco ACS, etc, so termination has too many drawbacks to use IMHO.