Normally, an emergency tiller is only required if you have wheel steering. The steering cable could snap, or come off the quadrants, etc., in which case you'd be in big trouble without a backup emergency tiller.
Somewhere I have a copy of the ORC equipment regulations, but my "fail safe" filing system seems to have deserted me, so I'm doing this from memory only. On boats like ours, with a wooden tiller, the ORC regs MAY require the we have a non-breakable (metal) emergency tiller aboard. If so, a piece of 1/2" pipe with a couple of flanges welded on to fit onto the rudder would suffice. I'd say this is a very low priority item. Modern laminated wooden tillers are VERY unlikely to fail.