Arabic coffee is a symbol of generosity in Saudi society, and it has manners that old and young people know. People roast the coffee beans over a gentle fire until their color changes. Then they grind the beans and boil them with water. Sometimes they add cardamom or saffron. The host pours the coffee with his right hand into small cups. He starts with the guest who is oldest or most respected. He fills the cup only a little, so he can serve the guest again and again. When the guest wants to stop, he gently shakes his cup. Dates usually come with it to soften its bitter taste. People still serve it in gatherings, at celebrations and when they welcome visitors. UNESCO has listed Arabic coffee as part of the intangible cultural heritage of humanity.

Question: Why does the host fill the cup only a little?