No I think the GP meant the port on the iPhone as the “other end”. In other words, why not have all of the protection logic built into the phone?

just as an example, imagine you end up putting a fuse in the cable. If the fuse blows, then the cable can be easily replaced. A chip in the iPhone.... not so much.

Though likely there's something in the phone _as well_ as the cable.

If the cable is dumb, it can’t switch the +5v power coming from a USB supply. If it can switch it, it’s not dumb.

So we should buy expensive cables and cheap power supplies?

Those cheap power supplies are ubiquitous, so it's more about Apple building their cables to exist in the built environment than dealing with the fallout of consumers busting up their expensive phones by charging them on whatever's lying around.

Guarantee there was a consumer study where they compared reactions between these scenario.

The manufacturers knows that if it’s their product in contact when a user is shocked, they will get some blame even if it’s “really” the sketchy power supply’s fault. And since some cables have these safety features already, anyone making cables without them will appear extra negligent when bad things happen.

The world is unfortunately not very efficient.

There was already a huge installed base of cheap power supplies