More people are becoming more advanced users.  I like to think of it in terms of a math equation.  User + Purpose = OS.  For example:

 

Noob, just point and click + Web and email = Windows

 

Noob, just point and click + Web and email at work = Windows (Pro)

 

Power user, still mostly point and click + Web and email = Ubuntu

 

Power user, command line literate + Web and email = Fedora

 

Sysadmin + basic nonessential services = ANYTHING, doesn't matter.

 

Sysadmin + essential services = RHEL, CentOS, BSD

 

Satellite systems engineer + Mission critical ground console = HPUX

 

Or something along those lines.