Comment by core-questions

> more or less a replacement for AD if your clients are unix based

Few people are lucky (?) enough to support a purely unix environment. AD is not expensive when it comes to enterprise-scale projects and plenty of things simply require it for proper support, so I've never seen an enterprise that doesn't have it. I have seen enterprises with classic non-AD pre-Windows-2000 LDAP integrated alongside AD, but usually just as a legacy thing that's too hard to remove.

Considering the amount of resources available to help with AD vs. the amount you'd need to be able to support a 3rd party solution, it should be no surprise MS still has a stranglehold on this. What's more surprising is how badly they've fumbled the use of Azure AD, SSO, ADFS, etc. as real solutions compared to the cloud-first vendors like OneLogin, Duo, Centrify, etc.