Re: The only reason "everyone" runs Outlook is because "everyone" uses Exchange.
Samba is used for SMB/CIFS file access. It works. And a lot of devices have it (most is pushing it... most Android tablets would never ship with Samba by default, there are apps to be SMB clients, for example - sure, NAS, media centers maybe, etc. but otherwise no).
But that's just one tiny feature - with no authentication whatsoever. That's the "home user accessing the computer that's open to the entire network" feature, not any significant usage of SMB/CIFS that even a basic NAS would implement.
Centralised storage relies on authentication. Authentication relies on Active Directory/LDAP/Kerberos integration. In the case of Samba, those things aren't "standard" LDAP/Kerberos, I believe (correct me if I'm wrong, but didn't Samba have to ship with its own implementations? That may have changed now, but the days of things like LikeWise Open etc. it was necessary to install completely different and separate versions to the LDAP/Kerberos software that came as standard on most distros).
Samba touts itself as:
"the standard Windows interoperability suite of programs for Linux and Unix.... secure, stable and fast file and print services for all clients using the SMB/CIFS protocol... an important component to seamlessly integrate Linux/Unix Servers and Desktops into Active Directory environments. It can function both as a domain controller or as a regular domain member."
You're talking about unauthenticated (or trivially authenticated, i.e. local computer logins) access to a share... but the software is claiming to offer an interoperability suite for Linux/Unix machines, as well as AD integration and domain controllership.
Additionally, although such SMB/CIFS isn't trivial to implement, it's literally just a tiny and necessary first step to any kind of network integration. It's literally not even enough to log into a network shared drive, for instance, rather than a home shared drive. Samba have had "co-operation" from Microsoft enforced by an EU court, not to mention EU funding, and DECADES of developer time put behind them. And they fulfill one tiny component.
Sure, the software gets used a lot for that (basically the equivalent of "smbclient" functionality, as was), but Samba is claiming to be, aiming to be, and has for a long time wanted to be, a lot more than a network filesystem interface. And yet it still can turn into a nightmare to, say, get to \\domain.com\netlogon ... AD auth, DFS, internationalisation, ACLs, etc. all kick in on even the most bare basics of "trying to get your Unix machines to talk to Windows machines".
There are no domain admin tools. Not even an "AD Users & Computers" equivalent. We're told to "just use the Windows tools" (I'd actually pay more for a Windows AD management tool set that worked on non-Windows computers, than I would for a software that let me set up a Windows AD running on a non-Windows computer). So you can't run a Windows-style AD using Samba alone, without having to manage users extremely manually.
The fact is, 27 years after initial release, 15 years after "Active Directory Support" was listed, it's still not there for anything other than a bog-standard, simple-passworded share - something trivially achievable with TFTP, let alone NFS or similar alternate technologies. But we have "Apple Time Machine Support" and Btrfs-compression!
I have created, managed, and decomissioned entire school networks reliant on Samba and projects like Likewise Open (as was, it keeps changing names) - one school we had netbooks that authenticated against the AD via PAM. They "work". If you're prepared to accept a whole bunch of caveats, severely limited functionality and manageability.
The reason is that it's incredibly hard to follow the protocol. Even just keeping the barest of "I'd like to access \\server\folder\filename" functionality working, up-to-date and secure takes up a vast chunk of developer time once it involved integrating with a fast-moving proprietary product that has to be reverse-engineered.
P.S. There's only one command in Window Powershell that I use with any regularity. The modern equivalent of ntdsutil to promote/demote DCs (I never remember the commands and have to Google them each time, that's how often I use them). Given that I administer Windows networks for a living for the last 20 years, using that as an attack on Windows is really quite weak.
Fact is, I can create and permission a user in Windows AD in seconds, including fine-tuned delegation of AD editing rights to the user, and all kinds of settings, group membership, inheritance, etc. It's just not possible in "Samba"... certainly not without an entire swathe of commands typed in on the console - and in a Samba-only environment, I'm not sure it's possible at all (you need AD Users & Computers running from a Windows machine?).
What you have is the equivalent of saying "We have Microsoft Office" when what you really have is a command-line tool like antiword that parses a .docx file for text. Sure, that may be "all most people need" but it's certainly not what's been advertised for the last 15-27 years.