Why? Because, no offense, but I don't want to be "friends." I don't know you, I may like your work or may just be learning about your work, but I would prefer to lurk and follow rather than be totally engaged as if we know each other as buddies.
This is important for so many people who don't have a fan page but who do have a personal page.
I've noticed that people over the years who have asked to "friend me" and whom I declined, are part of my "followers" -- that is, they can follow along with things I post publicly, rather than things I post for my real friends who I engage with.
I'm conscious of this fact and every once in awhile, I throw them a bone, well, I don't want that to sound rude, but I will post malignant things that aren't so important as to give my location or any personal info, you know, like, "Isn't this sunset pretty."
Hey, sounds boring, but people are following for some of these pearls of wisdom.
So to allow people to follow you, I've copied the Facebook rules here from their instructions page:
How do I allow people to follow me:
Friends follow you automatically and can see your posts in News Feed. You can also allow people who aren't your friends to follow you:
1) Go to your settings
2) Click Followers in the left column
3) Choose Everybody next to Who Can Follow Me
Your Followers can see posts you share as Public in News Feed.
My Tomversation comics pages is here Facebook.com/Tomversation - I post comics, but also other comics related material and pop culture stories.