It's called "marketing" (and is sometimes vitally important)...

From snopes.com, a certain wisdom:

In the wake of Cooper's chicken incident, the rumor flew around he'd torn the head off a live chicken and drunk its blood during a show. Upon hearing it, Frank Zappa placed a call to Alice Cooper:
"Did you really do that?" Zappa asked. "No," replied Cooper. "Well, whatever you do," Zappa said, "don't tell anybody you didn't do it."

Cheers...