Yes, they will try to monetize everything. But i don't see them hardwiring they're system to sift out those who don't hold a balance if that's not GW's primary purpose. I could be wrong, of course.
Not because they don't make money on them, but because using the service in that manner is a red flag of abuse. Pulling money out of the account and then sending the same amount you just pulled via credit card is obviously a points play. Otherwise, why wouldn't you use your GW balance to pay the person?
Personally, I don't mind leaving it there for a few days. Let everyone win. I don't need the money until the statement closes anyways.