When banks create money with a matching liability, they face the risk that the customer will try to take the money out in cash, or transfer it to an account at a different bank. In order to accommodate this they actually have to have the cash on hand, or borrow it from another bank with interest.

Likewise if you have 20,000€ on hand, or can borrow it from somewhere, you can use it to buy a car. You can then keep a mental note that you 'owe yourself' this money, but doing so makes no real difference.