In my experience Captchas are used a lot by inexperienced developers. As you stated, they are not particularly hard to circumvent, but they are incredibly easy

In my experience Captchas are used a lot by inexperienced developers. As you stated, they are not particularly hard to circumvent, but they are incredibly easy to implement. So developers just install a Captcha and outsource the problem to Google. I think the primary way to deal with the problem should be to design services in a way to make them unsuitable for spammers.