Many people who use Facebook for personal and work reasons struggle to find the balance between sharing somewhat personal info with friends and sharing with the world. Creating and maintaining a separate page is a boatload of work and, depending on the size of your following, may not be worth it.
In the past, you pretty much had to make the decision- do I make my life public? or do I just shut out everyone I don’t actually know? Most people elected to keep their friend list to those individuals that were close friends and thus, they were not able to enjoy some of the business benefits of growing your network and personally branding yourself.