"Work Friends" or Just "Friends"?

I wonder why we use the term "work friends"? I was lying in bed thinking about this one night recently. Maybe because lots of life moments have been happening with my work friends. My work friends are my friends. I hope. And, why wouldn't they be? I spend more time with my work friends than any of my other friends, or family, for that matter. My work friends are the first and last ones to see me every day besides Adam & the kids. They're the first to know if something is wrong, the first to hear bad news, and the first to hear good news. They listened to me the many times I cried and worried about Baylor's hard times in school or, most recently, the 100 times in a row that I did the pro/con list about choosing a daycare for my baby. They share with me their problems and their kids' problems and their family issues and their newest little bundles of joy! My closest friends made throughout the years have been people I've worked with, and they are the friends I stay in touch with most often. So I concluded that, for me at least, there really aren't "work friends". I just have great friends that I happen to work with!