They want them because they're being lazy/cheap. No, seriously. They're called widowmaker cords for a reason, but inevitably some muppet with two plugs and some wire will come up with the brilliant idea that one of these will work for.

One really sneaky and dangerous place these get made are generator backfeed cheater cables for houses. You see them in RVs, Xmas lights etc too, but generator backfeeds are super dangerous because they're also juggling two potential power sources. A backfeed is where a house/building is disconnected from the grid just by flipping off the main panel breaker, then it's "backfed" by a generator going into another breaker in the panel. Usually, without any type of safety interlock to keep the mains voltage off when the generator is on, or vice versa.

Afaik, this is illegal per housing code almost everywhere that I've seen, but still every now and then some yahoo thinks "wait, if I make a two-ended cable and put a receptacle on the house, I can remove the generator easily without any of the expensive safety crap!" And then grabs a live male plug when they fuck up and didn't shut off the generator or mains voltage...