This goes hand in hand with our atomized modern existence: we don't know our neighbours, we don't have anything occupying the place churches used to have in terms of community building with the people who live around us, etc. so we replace it with workplace relationships.
Thing is, workplace colleagues are seldom actually your friends in the true meaning of the term. Many of us lose contact with 99% of the people we worked with when we switch jobs. A friend is someone whom you have an ongoing relationship with independent of where you live or work, I think.
