I think everybody here really does know the real reasons why this and that is done a certain way.
Perhaps altimeters will be with us for ever, because they are simple and don't need a power supply.
But I can see one day everybody flying a precision altitude, GPS/EGNOS/WAAS derived. It would dispense with RVSM (which adds at least $100k - a totally mad and ludicrous amount for what you are actually getting for that money in equipment terms - to the cost of any plane capable of climbing up there, and a lot more than that to upmarket types) and would do away with QNH, QNH readbacks, the need to pay the salary of ATC staff reading out the QNH, etc.
One day, in CAS anyway, clearances will be delivered digitally and it would be silly to have a mechanical altimeter, with a servo motor driving the subscale knob, and the servo motor controlled by a computer which decodes the ATC message
