Witten is far from the worst Pro Bowl alternate we've seen. Vince Young and David Garrard made it one year because literally everybody picked ahead of them bailed.
It's 100% a name/rep pick though.
That means you think the players and coaches are going off of his former reputation, too. That's unlikely.
The better answer is the guy is still a pretty good player, and other players and teams know it. It also explains why they run after him when games are over to let him know how much they respect him.
11 probowls is rare air. We ought to just enjoy watching his career instead of be rushing for it to be over so some schlub the likes of Martellus Bennett can try to take his place.