Why do we say "It sucks", not "It's sucks"?

Why do we say “It sucks”, not “It’s sucks”. I know actually it’s a verb, so why we add “-s”?

Because it is a third person pronoun and suck is a verb. For example, she talks.

Sorry, I’m sleeping now xd. I am not believe I’ve added this question. you know in polish it’s translated as if it was an adjective.

sorry
hope you aren’t terrified :))

People say, “It sucks,” because the expression began as a very obscene reference to oral sex. “Suck” is a verb here, and originally in the expression there was a direct object.

Many people who remember the full expression find the use of “sucks” in this way disgusting. You should be VERY careful where you use it, because for many people the expression is quite vulgar.