That is their whole point. As an alternative Captcha Method, they double the risk of false positives being abused by bots but likely due to anti-discrimination laws against the disabled, they are necessary. The solution: make them impossible to solve so you follow the law without exposing you to any risk of false positives. After all, who's gonna believe a cripple that googles captchas are impossible. Must be their fault, they are disabled after all!