Non-standard variants of English grammar are very common in popular songs. There are two main reasons for this- - They often sound better. 'Don't' may fit into the rhythm of a line far better than 'doesn't'. Likewise 'ain't' may sound better and fit into the music more neatly than a standard/correct grammatical form. - The songwriter may want to sound cool, or rebellious, or casual, or angry...any of these can be suggested by the use of non-standard grammar. Enjoy the music, and sing along if you want to. But don't use these forms in ordinary speech. 'He don't' and 'I ain't' is fine in a song lyric, but not in the real world.

You're right, the song is not grammatically correct, it should be *doesn't*. As with a lot of pop culture (movies, songs or spoken word), the artists take a lot of "artistic license" and play fast and loose with the grammar.

honestly I think its just the singer having fun and purposefully using the grammatically wrong version.