Having a reminder cup will make life easier and your mother happy. As it is customary to leave the nest when you grow up, it is a nice gesture to call your mother on a regular basis.
When you live on your own, you get lost in the hustle and bustle of solo life. It becomes very easy to lose track of what's important in life, such as your mother. There is nothing in the world that is more important than a mother's love and the 'call your mother mug' will help remind you that you should do a good deed and remind her that you are still alive and she is still an important factor in your life.