Why do they need my details for a purchase?

At the cashier i am asked my name, surname, cellphone number. Why? Why must i provide these details for a purchase? I am not buying weapons of mass destruction. <br> I do not like to be asked my details especially while in a public area where other shoppers and staff can hear my details. Having been a victim of ***** i challenge Sportsman's warehouse to stop this ridiculous practice of soliciting information.<br> Further, pretending its for warranty as i am told, makes it worse. Again, the warranty has nothing to do with who owns the product!