I would pay $1000 to take one test so that I don't have to do another one for at least a decade. There's some real money to be made in selling the idea of accreditation to employers.
Bar exam and MCAT exam prep industries do seem to make good money in some states some years. An appeal to capitalism isn't the worst idea for how to sell the idea to employers.
(ETA: Though arguably it is exactly how we got multiple companies like leetcode that are building the worst of both worlds, the standardized testing and extremely spotty employer buy-in across a handful of non-federated competitors.)
Leetcode is just based on the wrong premise. No one has to be a good developer or engineer to do leetcode. Even the people who run Leetcode don't need to be good engineers. Hosting a bunch of reductive code puzzles is a lot easier than creating structured exams and proctoring them. This isn't to say that the latter isn't feasible, but the incentive is there to fool the industry into thinking that the ability to solve puzzles is a good metric for technical skills.
(ETA: Though arguably it is exactly how we got multiple companies like leetcode that are building the worst of both worlds, the standardized testing and extremely spotty employer buy-in across a handful of non-federated competitors.)