Why is that a feature? ...interesting :) Our stoves here usually have some heat-based protection, where you have to hold the knob pressed in until a tiny rod heats up (usually 2, 3 seconds) and after that you can release it and the gas will stay on. Without power, you just need a ligher (or anything releasing a spark) to ignite the gas. Also, the default configuration for gas stoves is 3x gas cooktop + 1x electric, so most people are covered in both cases.