It's the lifeblood of enterprise IT. The AD manages everything that is concerned with authentication and authorization, not only of actual employees but often a

It's the lifeblood of enterprise IT. The AD manages everything that is concerned with authentication and authorization, not only of actual employees but often also of service accounts (servers). If it's not managed through the AD, it's often not allowed to exist. It's also (legitimate or not) often the reason to go for a microsoft tool or (azure) service, because it 'integrates more easily' with the access management stuff that is in place.