Why? 20 ms is a very long time in the world of digital electronics. 1 MHz = 1 microsecond ticks, and most embedded MCUs run 10x to 100x faster than that. Sensors and ADCs commonly have microsecond-range response times, too.

The mechanical part (rapid inflation) is more interesting, but for a long time, they did it the "obvious" way: a precisely-calibrated explosive charge, just enough to fill the bag without tearing it apart. Now, I think they're moving toward compressed air, which probably requires some clever engineering to build a sufficiently responsive electronically-controlled valve.