I'm not sure if this is still true, but the lock that Outlook + Exchange had on some parts of industry was impressive. Many people felt there were serious problems with Exchange, but people continued to use it because they didn't know email servers, they just sub-contracted that out.
I agree with your comments about average employees. But perhaps this is changing? People are used to different messaging systems now, with various social networks and smart phones exposing them to better (or at least different) ways of communicating.