A currency which gains value encourages holding it, agreed, however, there are opposing economic forces at play as well.
First, the marginal utility of additional units drops for the hoarders, and marginal utility is a well established economic fact.
Second is the time preference of goods. People's lives are finite and they don't want money for money's sake, they want to exchange it for useful things. If you're really hungry, you will buy your sandwich today, not tomorrow even if it's going to be cheaper. Real world examples are electronics and the price of oil. Electronics get better and cheaper with time, and yet, people still buy today. Oil has depreciated hugely in the last months, and yet, people are buying gasoline and heating oil right now, even though signs point to it being even cheaper.
Taken together, you have the desire to hoard counterbalanced by these two factors, which creates a balance of hoarding and spending. This does an economy make.
I think the point is that it lives on a spectrum. If inflation was so bad that your savings would be worthless tomorrow, you would run out and buy as many materials goods and services as possible. If you knew that tomorrow it would reach 10 times its current value, you might go hungry for a day to cash in on that.
In either case, you're obfuscating the consumer's real demand due to 2nd order speculation. Using some particular good as a unit of account fundamentally introduces a distortion into the way that people elect to spend / save. And many people have different takeaways from this fact. If you're a goldbug or a Bitcoin enthusiast, you think that inflationary pressure is evil and deflationary pressure is good. If you're really into Keynesianism, you might think that consumption is good and saving is counterproductive. If you're the Federal Reserve, you think there is a right amount of spending that expert economists should target by tinkering with the money supply.
For anyone interested, I personally think the real answer is to look for ways to design a system that removes the distortion entirely by introducing a currency that cannot be held. In other words, a financial system in which the unit of account, the grease in the gears of the economy, only exists in the brief context of a transaction. The actual holding of wealth would all be done using electronic "shares" of real material goods, sort of like what you're buying at a commodities exchange. In this world, people's personal savings would be electronic, hyper-diversified stock portfolios. The "currency" of this system, if you could even call it that, simply acts as a yardstick for understanding relative costs, rather than needing to understand the N^2 different exchange rates of a typical barter system. You would hold micro shares in thousands of different products thanks to automatic software tools that blended expedience with your desire to personally elect what goods you wanted a long position on. In this way, the appreciation / depreciation of your personal savings would rely quite transparently on current values of the goods it represented. Crucially, removing this layer of abstraction would make it much harder for your fortune to evaporate purely on perception of value (see: Zimbabwe) since you would never give it away for less than what the underlying goods were worth to you personally.
First, the marginal utility of additional units drops for the hoarders, and marginal utility is a well established economic fact.
Second is the time preference of goods. People's lives are finite and they don't want money for money's sake, they want to exchange it for useful things. If you're really hungry, you will buy your sandwich today, not tomorrow even if it's going to be cheaper. Real world examples are electronics and the price of oil. Electronics get better and cheaper with time, and yet, people still buy today. Oil has depreciated hugely in the last months, and yet, people are buying gasoline and heating oil right now, even though signs point to it being even cheaper.
Taken together, you have the desire to hoard counterbalanced by these two factors, which creates a balance of hoarding and spending. This does an economy make.