The speedometer shows IAS which is way more informative of what's happening to the aircraft than GS or TAS. IAS measures "the amount of air that hits the wings"

The speedometer shows IAS which is way more informative of what's happening to the aircraft than GS or TAS. IAS measures "the amount of air that hits the wings". As to altitude there isn't a single always applicable definition of "altitude" hence pilots have to adjust it based on their current task, there simply isn't a way around that. You could try to always use "true altitude" in WGS-84 or something, but that's far more complex than a simple pressure altimeter. For example it generally cannot be done without external inputs, such as very accurate pressure maps or gps-like navigation aids. More complex = more failure opportunity.