It isn't stupid, it's cheap insurance that your competitor doesn't gain access to your data. Yes there are ways to make sure Amazon doesn't have easy access to

It isn't stupid, it's cheap insurance that your competitor doesn't gain access to your data. Yes there are ways to make sure Amazon doesn't have easy access to it, while still hosting with them, but they are hard, and at the end of the day, physical access trumps most of those security controls. Also, Walmart are SUPER paranoid about their internal data.