Is that true?
Microsoft's ActiveDirectory, Exchange, and SharePoint are every where.
Perhaps they have different parts of "enterprise" pie.
In last 10 years, I have visited 100s of enterprise data centers and seen the transformation from primarily UNIX (non-Linux) and Windows server to Linux. Today I rarely come across UNIX and come across shrinking base of Windows servers. Ten years ago, I saw shops exclusively being either UNIX or Windows. Today shops are either Linux or a combination of Windows and Linux. In Enterprise OS market, Linux ate UNIX for lunch and now nibbling at Windows for dinner.
Active Directory and Exchange are much more popular because of its utility with windows workstation managements and user familiarity with PC and Outlook. With the acceptance of BYOD, thanks primarily due to iPhone and iPad, the MSFT hold on workstation side has started to be impacted.
Sharepount is not that much popular except in dominantly Windows server shops.
Most of the money is made on Windows Server licenses and many of these things get thrown in.
os, sql server, office/exchange.
Everything else is tiddly winks.
And most if not all of them have some kind of Office Document viewer and basic levels of editor, either built in, shipped with, or available as an app.
And how is Samba, a clone of Windows SMB file shares, going to help anything mobile?