There is no good reason in the Harry Potter universe for magic to be kept secret from Muggles. ANY moral character in that setting should be calling to end the divide so magic can be used to help wider society. The fact this is never addressed is an embarrassing oversight. It's made clear in the series that magic can only be cast by those who are born magical, but it's also made clear that magic still works on muggles. Lets think about just a few of the applications it could have for people in wider society: