Answer:
It demonstrates superior knowledge over other candidate, it shows time went into applying for the position, and it ensures the document is clear and readable.
Step-by-step explanation:
Taking time to check again all your spelling, formatting, and everything else on your resume only shows that you care about a well done work and that's why it is well seen, since the resume will most likely have no mistakes on it. It also, as described above, shows dedication and willingness to do a good job.