One of the main points of spending a weekend together is to see how well a couple can cope with each other in close quarters, and there should be few distractions during much of the time. It can be difficult for them to decide how well it went if unexpected company drops in. If those who drop in are parents, the results can often be frustrating and hilarious. Many children who have moved out of the house still want their parents to believe they are chaste, so hiding the fact they are spending a weekend with a date can be an unspoken goal.
Friends might also drop by to see how the couple is doing, but the situation can become very awkward if a former partner rings the bell. Even if they have remained friends, it can cause jealousy to be an issue between the partners. Those who want a great weekend might just hint they are thinking of going out of town, and that should halt the flow of traffic.