Why do writers revise their paragraph?

To check their grammar and punctuation to see if they made a little mistake because sometimes we think and write fast and not check it too see if it written correctly

Revision literally means to "see again," to look at something from a fresh, critical perspective. It is an ongoing process of rethinking the paper: reconsidering your arguments, reviewing your evidence, refining your purpose, reorganizing your presentation, reviving stale prose.