Second, if you look at the specs for a transistor, you'll notice that many of the ratings are specified as CURRENTS. Although we often use voltages as a reference in digital circuits, deep down inside they're really ANALOG circuits, which require a certain amount of current to operate. If you design for a higher operating voltage, you still need to run a minimum amount of current through the transistors to get them to switch. Do the math:3.3 V x 0.010 A = 0.033 W24 V x 0.010 A = 0.24 WMultiply those Watts times thousands of transistors in an IC and you can see where the power requirements (and heat) could quickly get out of hand.
Why don't CPUs and microcontrollers operate on 24v?
All the above, plus 24V lets the "magic smoke" outy-cool smile