I'm inclined to go with your alternative hypothesis. The quality of the captcha response degrades the more times you solve it consecutively. I was recently dev

I'm inclined to go with your alternative hypothesis. The quality of the captcha response degrades the more times you solve it consecutively. I was recently developing a web frontend that had a captcha implementation on the login form. The first couple times I solved the captcha there was no problem. Then once it got to fourth and fifth one it started making me solve a few of captcha pages in a row. Eventually it was forcing me to solve several pages of "Select the picture of the fire hydrant" over and over, often marking it as incorrect when it definitely wasn't, and then restarting back from the beginning so each run-through took multiple minutes forcing you to solve dozens of captcha pages before accepting it as correct. So, to add to your hypothesis, they're probably doing this intentionally not only to get more data for their AI algos, but also to mitigate people training bots on CAPTCHAs. EDIT: Also the fact that you're being downvoted is baffling to me but my tinfoil hat persona makes me wonder if it's some orchestrated downvote because you're pointing out a hypothesis that Google is trying to keep hidden.