Dialects tend to eliminate some of the complex grammar in standard language. In Standard American English, an s or es marks verbs in the third person singular present tense:
He, she, or it does not believe
But in Southern American English and African American Vernacular English, all verbs are conjugated the same way:
He, she, or it do not believe
This is something you've probably heard if you listen to American musical genres like country or rap.
In the Jay Z/Kanye West song "No Church in the Wild," Frank Ocean sings:
What's a god to a nonbeliever
Who don't believe in anything?"
Of course, there are many languages in the world that don't conjugate verbs at all, one example being Chinese.