TL;DR: YOU aren't supposed to work on a live circuit. Some have to.
May I point out that there are folks who have to tune, repair, or otherwise adjust live circuits ranging from single-digit voltages to hundreds or thousands. CRT monitors have a high voltage section driving the election gun; older ones had big capacitors which could retain that voltage after the set was turned off and unplugged.
Even low voltages can be dangerous if they have enough amps behind them and you accidentally short something. That's basically how a welder operates, after all. Used to be that many of us knew someone who tried to discharge a large capacitor (possibly in a TV) by shorting its terminals with a screwdriver and found it had welded itself in place.
None of this means most of you should be working on live circuits, or ones with big capacitors or high voltages. But the tools exist because there are use cases other than yours, and once they exist you can buy 'em.
I have one set of insulated screwdrivers. I rarely need that feature, but they weren't expensive and rarely is not never. They aren't the ones I reach for first, partly because I don't want to risk damaging the insulation when I don't have to, but there have been times when they were useful. But I'm a trained idiot... and in fact most of those cases were just to keep from inadvertently shorting something in a piece of electronics I was working on and releasing the magic smoke, not for safety.