Because it takes more than just one top tier talent to create a significant upward trend in ratings. Lesnar is seen as legit. No one else in the business really is. If Stone Cold returned he wouldn't bring the ratings back up either.
Now, if Stone Cold, Lesnar, HHH, Mankind, Undertaker, Jeff Hardy, Shawn Michaels, Sting, Hulk, Raven, Goldberg, Macho Man, Ric Flair, and Scott Steiner all came back at once, in their prime? That might be a different story. But even that's questionable given that today's generation of effeminate males doesn't really like looking up to men who are bigger and stronger and superior to them.
