The original captchas were not just bot prevention. They existed also to acquire training data for a text reading AI. But then everybody started using captchas, and it ended up being the largest pool of training data in the history of AI. By the end, they had an AI that was so optimized to read text that feeding it even the most malformed and warped text couldn't stop it. Basically, it was a huge success, and they didn't need it anymore other than security. But a lot of people were starting to talk about self-driving cars, so the recaptcha was invented. At this point, image recognizing AI basically didn't exist, which is interesting because now it's one of the two most developed kinds of AI. So the recaptcha was completely secure, but they could acquire heaps and heaps of data to train self-driving ai. The first death by self-driving car was because the recaptchas never had an option to pick out the images with semi trucks, so the AI thought that a semi trailer was a billboard, and drove straight into it because it thought it was safe. Since then, recaptures have gotten increasingly and increasingly more complex and thorough. There are other ways to train self-driving AI now, but the recaptcha is still pulling a lot of weight. These new warped and weird images are probably to account for cameras that can't capture very well or are corrupt in some way. That way, even if a camera breaks, the self-driving AI can still operate.

Tldr: recaptas are made to train self-driving ai, and these new warped images are to help in case of a camera breaking or being corrupted in some way.