Why don't people play jungle Kassadin?

In theory, this sounds like a pretty good idea.

- He's not super squishy

- He has both single target nuke (Q) and AoE (E) to clear camps

- He has amazing mobility and gank potential (R)

- He has an autoattack enhacer (W)

So my question is, why don't people use it?

Am I failing to see an obvious weakpoint in jungle Kass?