This is because when a bank loans out money in most modern countries they in turn borrow the money from a federal reserve bank which in turn just creates the money to be loaned out. This is how federal reserve banks create more money. The idea being that loans drive the economy through building businesses and infrastructure but it also has the side effect of driving up the cost (inflation) for consumers of everything that can be paid for with loans: houses, cars and higher education and most of those things don't grow the economy in the same way a business loan would.