Adding a Windows 8.1 pro client to a domain.

At my home, I run a Windows NT domain for file and print sharing (it's a long story, just accept it as true).  My son just bought himself a Dell Insprion 11-3000 laptop with Win 8.1 pro. (ooh shiny!)

After joining it to the domain, It could not read any file or print shares.  So I googled around to find the answer, but couldn't find an answer that seemed to apply.  A coworker I knew had used a Win 8 on the domain at work, so I pinged him.  His reply?

open powershell as admin.
Set-SmbClientConfiguration -RequireSecuritySignature $true

TADA!  It works.  Wow.  That's pretty arcane.  The fix left me with several questions.  The biggest two are:

1. What does this do?  Even the online help does not clear anything up.
2. Why was this not set to begin with on a pro version, intended for use on a domain?

Anyone?