I suppose the only question remaining would be "Are there any downsides from a technical perspective"?  If there's no harm in future-proofing, it seems like an obvious thing to do.  So I can't help but think that if there were no cost to doing it, it might have been implemented before now.  I'm guessing that perhaps it makes transactions larger if we have to store extra digits in the blockchain?  Another 4 characters to go from 8 to 12 decimal places may not sound much, but ideally we want transaction sizes smaller to aid with scaling.