In a healthy economy deflation isn't possible because the money supply naturally grows with the economy. This was true even when we were on the gold standard because banks will be more aggressive with lending, which effectively creates more credit money. The deflation has historically only occurred when a large quantity of credit money gets destroyed in defaults.

The purpose of money is to facilitate mutually beneficial transactions. When the money supply contracts, the "price" of money goes up. People are incentivized to hoard money for the sake of hoarding money, which adds friction to mutually beneficial transactions. This causes a feedback loop, which leads to even more deflation and even less economic activity.