I worked at RadioShack in the late 90's. We had to ask for name, address, and phone number. It was just part of the transaction flow on the point of sale. If we got resistance, we could just put it under a "CASH CASH" customer. I vaguely remember telling customers "it's so they can send you our catalog". RadioShack sent out nice heavy catalogs each year, which many people liked. Sometimes if we were busy or just lazy, we'd just do that anyway. While my understanding was that it was primarily for marketing purposes, it was also useful in that we could pull up receipts by phone number (in case you lost yours), verify warranty/extended warranty status, etc.