Why are gyros driven by vacuum and not high pressure air?

[underfire]

air pressure changes with altitude

[27/09]

air pressure changes with altitude

As will vacuum in this situation.

Remember it's the pressure differential across the instrument that matters, so as ambient air pressure drops the amount of vacuum pressure difference also decreases.

What is important is the amount of air flow through the instruments. To create the required amount of flow you need a minimum pressure differential. Hence the need for pressure/vacuum regulators on the gyro air system.

[underfire]

Soon, these types of gyros will be obsolete, as the new solid state gyros come into the market.

Like everything else, your MSFT game controller has a better gyro than your aircraft.