Some people expect others to put all of the effort into making a relationship work. This might work out well if you really like the person, but it will get old pretty quickly.
If you feel that you are putting in most of the effort in the relationship, you may want to pull back for a while. Next time you run into the person they will inevitably ask, “Why haven’t I heard from you?” Both of you have arms and can pick up the phone to get in touch.
If you friend wants to know why you haven’t been in touch, let your friend know that friendship is a two way street with one of our great comebacks.