Humans are fickle creatures and money is the most valuable non-emotional asset to human life in the civilised world. We've all heard the phrases about how money makes people do things outside of their character, and someone who has free access to your money can do anything with it. And if they did take money you can't get it back because you willingly gave them your account details. If you want to give someone money instantly you can do it via instant bank transfers, they don't need to withdraw the money directly from your account under any circumstance.