Why do not all sites have captcha?

Question

CAPTCHA

Actually the essence of the question is in the title, why do many sites not have captchas? Not in the comments field, not during registration.. After all, it is easy to write a script that registers hundreds of left accounts on the site at once, did not have time to look around, and the database is already in bots. The same thing with comments, it's easy to make a script to leave comments with ads from different bots in different topics. Lack of captcha - laziness, negligence of developers, or lack of understanding why is it needed? It will not be difficult to embed it (even at least the most banal one, with numbers). Or maybe there is such a thing that the captcha is really superfluous, and I just don’t understand something?

Answer 1

1. There are other ways to protect.
2. There are captchas that are not visible to the user ( https://www.google.com/recaptcha/intro/)
3. It can be redundant

Answer 2

Captcha is redundant by definition. It interferes, annoys and does not make life easier for the user.
And only forced evil to weed out the most stupid bots.
Let it go. Normally made basis plus-minus lyam users - not a question.
This is more difficult. If there is user-generated content, then first people are needed who will moderate it (do not forget to make a clear moderator tool for searching and deleting a bunch of comments according to a template). Anti-spam automation does not eliminate the need for people to check manually. Have you seen spam on stackoverflow? And it comes across there.
And captcha, of course, is not a panacea either.

Answer 3

Captcha is a conversion killer!
Filters are everything!
Even trite: stumper.ru/use/isText to exclude links.