One more thing, about chains and automobiles: it's in many ways not a valid comparison. Additionally it seems to me car winter chains are being used if a) studded tyres are not street legal (most of Central Europe) and/or b) winter season doesn't warrant changing the whole set of tyres (it's either too short or too spotty) and/or c) you only need them for a short distance in low speeds. Around here, it's far easier just to swap the tyres and be done with it for the winter months.
--J