why do u never hear about some book authors winning anything?

[PokerPaul]

If they are such experts at the game, and are writing and selling all these books and the advice they dispense, wouldnt you think you'd hear about them more often in poker circles.

Specifically, i'm talking about the likes of Mcevoy, Caro, Vorhaus, silbenstang. They ahve tons of books out, yet i have never heard any of their names amongst big tournament finishes over the last 5-6 years, and i don't hear about them being in any huge ring games either.

Don't mean any disrespect, just an honest question...are they maybe just experts for lower limits type players?