Those were not "vision models" in the modern sense, but rather crude classifiers or OCR systems that were heavily dependent on human labor to handle many cases,

Those were not "vision models" in the modern sense, but rather crude classifiers or OCR systems that were heavily dependent on human labor to handle many cases, because the vision models of the time sucked and were hardly capable of anything. The economic value of CAPTCHA-based data labeling went to zero when AlexNet (the first general-purpose vision model good enough for real-world use) was released in 2012; from then on, you could just have the machines do that work instead.