To give lagniappe (pronunced lan-yap) is an old custom of the New Orleans area. It involves a merchant or tradesperson giving a customer more than the bare aspects of the deal. For example, a grocer may throw in a bunch of parsley or cilantro or some gum, a bartender may have a plate of goodies for the customers to taste, a baker may put in an extra doughnut in a dozen, or a druggist may have an art calendar suitable for hanging.
I think it's a gentle form of cultivating social capital by attempting to give the customer the sense that he's appreciated. Doing business is not only for the money, but is also for the relationships. Part of doing lagniappe is in the conversational exchange. While this takes time, and some impatient people might find this a bit much, it does serve a purpose in providing some loners with a level of contact that is within their comfort zone.
I hope lagniappe will persist as a social grace in the future.