Sturridge has been playing in the FA Youth Cup a lot though, maybe thats why he's not on the bench. Remember he was out injured until January. Sven recognises his talent but does not want to rush him back too early, he even admitted he's scared he'll get injured again.
Sturridge does play in the hole, yes, but I think that is why he isn't involved right now. Elano is in poor form, but I think Sturridge is a bit more attacking than him, and playing Sturridge supporting Benjani would maybe be too attacking. I'd still like to see him on the bench though, there's no denying that.