Why not? Because the Jets could still make it to the Super Bowl, and there's a very remote possibility Revis could be healthy by then.
The Jets will wait for Revis to have surgery – still a week or two away – and reassess the corner then. Said Ryan via the New York Daily News:
"Obviously, we're not going to put him out there if he's at risk. Let's just put it this way: if you're fortunate enough to make it to that big game and he's fortunate enough to be healthy, I know our fans would want him playing just like I would want him playing."
Still, Revis recovering from an ACL tear in roughly four months plus a Jets trip to the Super Bowl seems like a pretty unlikely set of circumstances.