It increases the return on investment needed for a project to succeed. Simple example: I grab the 100btc and buy machinery to support my new factory. Right after buying, I'm losing money, because machinery won't appreciate like BTC does. So, I'm only interested I machinery investments that return over the BTC deflation rate.

This is a simple example. Some of this already occurs in the real world, since machinery depreciates over time. it's just that currency deflation is another force opposing investment and braking money flow.