This is very common in many cultures and drives many of us to madness. But statistically, it is a proven negotiation technique for closing. This negotiation technique is in play if more than a few asks are made in a short period of time, or when no new information has been given that would potentially change the offer. The reason this tactic is used, regrettably, is that it works for the people who use it: they can wear people down. This is not a recipe for a durable deal or long-term relationship.