Capital can make money because it increases productivity. If you use your 10,000 quatloos to buy a machine that makes a worker more productive, your reward comes from the interest on that. Everyone can increase the value of their savings if everyone does this.
If everyone is hiding their quatloos in the mattress, there is no input of capital to increase productivity. Yet a deflationary spiral exactly encourages people to hide their quatloos in their mattress. Why bother taking even minimal market risks when you can make 10% from the growth of the rest of the economy?
And economies can grow not just from increased productivity.
EDIT: As a fraction of total buying power you are still were you were before.
This is a really, really, really bad idea.
If I have shillings equal to 5% of GDP, and I put myself into cryosleep for 100 years, there is no reason I should expect my uninvested shillings to still have 5% of GDP. This is a child's view of an economy.