I normally wouldn't bother since I hate pushing my views on people (and I'm just there to buy food after all). But she asked me 3 times in a row and after 2 "no"s I decided I might as well try to explain why. It didn't make a difference and I left with a signup form I had no intention on filling out. Such are the downsides of being naturally polite. I guess I could just keep saying no and refuse to elaborate.