Why do we search for special occasions to remember other people or relationship?

It would be nice if this was something that we did daily, and gave everyone that we cared about the attention and appreciation that they deserve. However, in daily life, it is easy to get sidetracked by taking care of our own needs, wants and desires, and sometimes there is not the time to take special notice of the people we love and care about. Special occasions give us a reason and occasion to remember to do this at least once a year (birthday), and more if that person is a special relative (spouse anniversary, mother's day, etc.).