1) Computer vision got a lot better over the past few years. It's also become way easier for the average Joe bot operator to run cutting-edge stuff. OCR tasks don't cut it for distinguishing people from machines any more. Every time I see a blog post about a new computer vision architecture or how some random developer trained a neural network to get an X% result on benchmark Y, I think to myself CAPTCHAs are going to get more annoying.

2) The frequency at which most people have to solve a CAPTCHA has gone way down. In the beginning, I remember having to solve a CAPTCHA every single time I did anything on some sites. Now, I can't even remember the last time I had to do more than just check the checkbox. So, the amount of annoyance is amortized over a larger number of sessions, and Google probably feels like they can ask the user to complete more tasks as a result.