I disagree. Adding Google's captcha is a 15 minute exercise. If i remember correctly, you copy/paste a snippet then add a callback in your own code. Whereas rolling your own captcha implementation would take much longer and be worse.
And it is this very convenience that has countless sites using it. As I said, there are other systems which are just as easy to implement as Google's and which are not overkill and also more privacy friendly (Google's CAPTCHA is known to fingerprint the user using heuristics like mouse movements, screen resolution, etc).
> there are other systems
Like what?
There are many easy to use libraries specific to different languages(like https://www.phpcaptcha.org/ for php) and frameworks. These are not as secure as recaptcha, but in most cases does the trick.
There are also services similar to recaptcha like solve media and hcaptcha. I believe hcaptcha is a drop-in replacement(https://hcaptcha.com/docs).