We can’t, this is a Red Hat choice 
we can only suppose this is due to compatibility issues with many software.
Exactly.
Again, you’re right. RHEL is not pushing Samba 4.
No, FreeIPA is not conflicting against Samba4: they are two different products with different targets.
(In my very personal opinion, I would like to stay away from any MS-related product as much as possible! So, bye bye Samba, FreeIPA you’re welcome!)
I think the response from Davide is very clear: Samba 4 can’t be shipped with CentOS 7 unless you recompile the full Kerberos stack.
Our main goal is to stick with upstream as much as possible.
But our customers ask for AD replacements for ages, and the only tricky, non-invasive way we found is a Samba 4 container. I would describe it as a necessary evil 