Tokenless Authentication Requests
If your GitHub Enterprise appliance is configured to use LDAP authentication, then every request against GitHub requires an additional request against LDAP.
At best, this delays GitHub requests because GitHub needs to wait for the LDAP requests first. At worst, GitHub requests will fail if the LDAP requests fail (for instance, because the LDAP server is overloaded with requests).
To avoid these problems, users should use personal access tokens (via HTTPS) or SSH keys to authenticate. GitHub will check those without additional requests.