What are the main reasons to not use Azure AD?
The ones I can think of are for managing desktop PCs and servers etc.
SCCM requires local AD.
Enterprise PKI requires local AD.
Centrally managing Windows servers in general requires local AD.
It may be technically possible to manage Windows 10 desktops in a large office that are only Azure AD joined, but why would you want to do this? If you have hundreds or thousands of desktop PCs all located in the same building, why would you manage them and have all these users authenticating into their workstations through a WAN connection to the cloud instead of from your gigabit local LAN connection? Why only have the more limited management capabilities of Intune vs AD group policy and then also have the extra licensing costs of Intune on top of all that?
Are there workarounds for any of the issue listed above?
Are there any other scenarios not mentioned that require at least hybrid AD instead of full Azure AD?