Since people talk about the things that interest and captivate them, why do believers talk so sparingly about Jesus?

While topics of conversation vary among adults, it is always true that people in groups talk about what is interesting to them. Even the quietest person will, on occasion, speak about things that are important to him or her. Some like to talk about ordinary events, while others enjoy discussing controversial issues. One thing is certain: what we say reflects what is on our mind. Subjects or experiences that captivate us will eventually find their way out in our conversation.

ESV passage Mark 1:35-45