Lord's Day Offering (1 Cor. 16:1-4)

One of the jokes that people make about the Dutch Reformed tradition is that every time the church gets together there is an offering.  This is exaggerated, but it is a perception that people have regarding reformed churches. There are other traditions who do not take an offering in the context of worship, but they put a box in the back of church.  So, why would we take an offering in the context of worship?