[Samba] Disjointness between samba and distros?

[Jeff Sadowski]

Most major distros compile samba with out the ability to do AD DC (Ubutum,
Fedora, Suse)
I'm not against compiling or going with a non major distro like Zentyal but
why do most major distros hold back from compiling samba with AD DC
support? (speculation is mostly what I'm looking for)
Fedora's documentation since samba 4.0 has stated
"We'll provide Samba AD DC functionality as soon as its support of MIT
Kerberos KDC will be ready."
This is even provided in 4.4.0rc1 build of samba for fedora 24(rawhide)

I'd rather see a document that says something like so

"Samba AD DC server compiled samba is incompatible with MIT Kerberos we'll
provide a compatible one as soon as samba supports MIT Kerberos KDC."

or something along those lines.

It just seems that samba has been disjoiint on its capabilities vs what
distros compile it for since 4.0 was released all that time ago.

What is going on in the linux communities?