It doesn't create an incentive to not spend money; it creates an incentive to not spend money wastefully, on things that provide insufficient value. That doesn't stop people from spending money for things they want or need. For most things people want or need, having them now provides more value than having them later.
After all, by exactly the same argument, why buy a computer today when you could wait and get a more powerful computer tomorrow? You could apply that logic indefinitely, except that the sooner you get a computer, the sooner you start getting value from it. At some point the balance changes, and you decide to buy one anyway.
