It absolutely is, but it is only applicable to large corporations and won’t help any SMBs. The issue is that this functionality via LDAP/SAML/OODS is frequently locked behind enterprise subscription tiers that usually represent an extremely high markup over other paid tiers.
Even in larger corporations, it often not possible to have SSO everywhere. We have multiple „shadow IT“ subscriptions for services that only our team uses. Most of them don’t offer SSO functionality, even for those who do a user base of 5 people is not going to be sufficient to have someone from the responsible departments deal with it. So we have passwords