Why can't I purchase an item at a store without giving my name and phone number?

Why do stores want my name, phone number and email address before I can pay for an item? This annoys me to no end. I just want to purchase a shower gel from Bath & Body and have to give all this information before they ring me up. Of course I use fictitious information, but why is this necessary? I end up scowling at the clerk, but of course it isn’t her fault she has to ask this stuff.