I'm no economist, but it seems like a lot of things (most, by dollar amount) I buy are simply not things I could feasibly defer for long. Food and rent (shelter) are the obvious examples by necessity, but also plenty of discretionary spending is obviously time-sensitive. I want to see a movie now, go skiing now, fly home for the holidays now, etc. It's unlikely that deflation stop me from making these purchases, unless it was some guaranteed short-term high-percentage deflation.
It doesn't take a big change of behavior if there are a lot of people doing it. If everyone reduced spending by just a couple of percent it would radically change the economy and growth forecasts (we'd be in a recession). Lowered growth forecasts would then incentivize savings, further pushing down future growth. There is no Bitcoin Fed that could cut rates and incentivize investment, a Bitcoin dominated world in recession would be a dire place to be.
