But with gas the difference is at least somewhat legible to the layman. You see the octane rating and know you're getting something for that extra money. With cables they all look the same to the uninitiated, after all it connects doesn't it? So people are going to go for the cheaper option because they can't discern a reason not to.
The type of person who owns a 5090 must also be the type of person who knows about the 40 series and it's cable problems. Little timmy building his first PC wasn't camping outside of microcenter for a week just for a chance to spend $2000 on a video card