Being human is not enough to read these captchas

I’m human, but being human is not enough to read these captchas !  I understand that these captchas are a must thing for websites, but i can’t understand why these captchas are too hard to understand ! Look at the most weird captchas i saw :

(A CAPTCHA  is a type of challenge-response test used in computing as an attempt to ensure that the response is generated by a person.)