But you would then need to bring it down to the low voltages required by the chips and that would greatly increased cost, volume, weight, electrical noise and heat of the device.
Look at the PCB of a 4090 GPU; you can find plenty of images of people removing the heatsink to fit water blocks. They literally have 24 separate transistors and inductors, all with thermal pads so they can be cooled by the heatsink.
The industry could change to 48v if they wanted to - although with ATX3.0 and the 16-pin 12VHPWR cable being so recent, I'd be surprised if they wanted to.
I guess the problem is not only designing the cards to run on the higher voltages but also getting AMD and Intel on board because otherwise no manufacturer is going to make the new power supplies.
It may be marine market specific, but several manufacturers limit to 36v for even high amperage motors because of it.
Obviously I=V/R will force this in the future though.
Going from 12V to 48 means you can get 600W through an 8-pin with a 190% safety factor, as opposed to melting your 12VHPWR.
But anyway for consumer products this is unlikely to happen because it would force users to get new power supplies which would reduce their sales quite drastically at least for the first one they make like that.
The solution would maybe be to make a low volume 48V card and slowly move people over it showing them it is better?
Anyway this is clearly not a case of "just use X" where X is 48V. It is much more subtle than that.
I wouldn't be shocked if someone told me that Nvidia already sells more 48V parts than consumer 12V parts.
But i'll also say - outside of heat, all of the things you listed are not safety concerns (obviously, electrical noise can be if it's truly bad enough, but let's put that one mostly aside).
Having a small, cost efficient, low weight device that has no electrical noise is still not safe if it starts fires.