Why doesn’t every UI Login include Captchas as the major security mechanism?

Captchas are the coolest inventions to avoid brute force attacks. Any attempt to try out different password combinations in an automated manner is right away blocked. Now I wonder, how come there are still many sites that doesn’t implement this basic security mechanism for their logins. Here is my dig at some of the advantages and disadvantages of using captchas, what is your story?

Advantages:

1.       Straight away avoid any brute force attacks.

2.       Login process cannot be automated to crack

3.       Can avoid account locking which is much more painful process

Disadvantages:

1.       Time consuming process during login, annoying and strain to eyes

2.       Some captchas are very scrambled to understand in first pass

3.       Many captchas are already cracked