Why do they keep using captchas when this test of humanity has such a major flaw and there are so many people with this degree of visual disability who can stil

Why do they keep using captchas when this test of humanity has such a major flaw and there are so many people with this degree of visual disability who can still easily use computers? Don't programmers know there are laws against that? I know they don't care but to choose it as a means of proof of humanity - a test considered illegal in many countries - seems truly backward of technology.