Having just got back from a ride with a very slightly off-centre stem that bothered me more than it should I'm wondering why steerer tubes aren't splined. They wouldn't need the full treatment, just a single groove up the front would do it. The dimensions could be standardised across brands, it could be so shallow that it would have no impact on strength, and it would be completely compatible with existing non-splined stems. The standard could even be based around a matching a shallow groove in the stem with a small diameter rod or bar used while fitting to align the stem with the steerer, as this would then mean that all stems were compatible with all steerers.
Or am I being stupid...?