why do we kiss when we are leaving???

This is the sign of expressing love to the leaving person. By kissing we keep on remembrance of someone. We kiss to those who are more nearer to us, not all the guys. Someone may say it tradition as we do not know the actual date when we started this. Actual this is western tradition. In India around 20 years back this tradition was not popular but now a days it is popular and a part of tradition. This has happened because of mixing of different cultures. It is good too, as we should always welcome good tradition.