Why some people don’t talk too much??

In our everyday life, we notice some people talk much & some are talking less. Some enjoying themselves to talk with others. But there are many people around us who talks less than an hour in a day. Does we know why this happened or why they behave like this? This is because their is a disease called stammering. Stammering is such a disease in which people whom has this can't talk freely. Sometimes they take 10 to 15 seconds for talking a single word. That's why, some people feel bother when this happened & the man whom has this disease felt him as a looser. I am also who suffered with this disease from a long time and still suffering. But sometimes I think God is the creator of this world and he will save us from this disease and from them too who laugh at us.