Deflationary currency competes with investment, not with consumption. For example investing in infrastructure, is a safe, low return investment. in single percentage digits. If the deflation of the currency is faster than that rate of return, then nobody will ever invest in infrastructure. People will never install solar panels on their house, etc.
EDIT: to add onto that answer, I'd say that just as there are still savers in an inflationary environment, there will still be consumers in a deflationary environment. Incentives matter, but are not absolute drivers.
If you said "It is counter intuitive with Keynesian economic theory", I'd see your point a bit more. But different schools of thought like the Austrians view the importance of short-term consumption differently than what is a sort of textbook model of the world.
Is it harmful though? Whether this is a good or bad thing might come down to how much importance you place on random consumption vs capital investment as the real engine of society. The Keynesian viewpoint is more favorable towards the importance of random consumption, the Austrian mentality would put a lot more weight on the value of saving for future investment and building.