No, sadly you're not wrong. That's exactly it. Captchas are getting harder and more counterintuitive because Google is using them to train their "AI" algorithms for automated driving and similar projects. Basically, those parasites are using half the internet users as unpaid "Mechanical Turk" workers.

That's not so bad as is the fact that they probably use the captcha apis to vacuum all they can from our profiles as well. See, for instance:
https://www.businessinsider.com.au/google-no-captcha-adtruth-privacy-research-2015-2

Quote: "The reCAPTCHA gives Google a very high level of entropy when it comes to distinguishing an individual”.

Google. Not even once.