For me at least, it's not about hiding or not asking. I've asked to camp many times, and with rare exception folks say yes and the experience is good.
Sometimes, though -- especially if you tour without much of a script -- you wind up in a place where you'd like to camp but there's nobody around to ask. Or there are people to ask, but it's an uncomfortable place to spend the night. That's when it's valuable to be comfortable with the idea of melting into the landscape for the night.