There are nasty consequences that can result from an economic environment where consumers hoard rather than spend their money. The most immediate problem is that businesses start to go belly-up when their overhead and expenditures outpace revenue. A deflationary currency won't help you when you get fired because the company you were working for can't afford to keep you on board any longer. Contrary to what some other here might have you believe, being deflationary isn't a magical ingredient that suddenly makes unsound money sound.
It's very natural to hoard as much something that is deflationary just as it is to spend as much something that is inflationary. But knowing fiat is inflationary, people still save. And knowing Bitcoin is deflationary, people still spend. The thing with currency is it works not because it's inflationary or deflationary, it works because its value is relatively stable. As long as the price remains stable with no drastic volatility, a currency can gradually be worth less or be worth more yet still serve its purpose, a medium of monetary value in exchange for goods and services. When the Zimbabwean dollar experienced hyperinflation, prices are so drastic that from the moment you pick something up from the shelves to paying it at the counter, the price could have already changed. That would be unsound money to you, a hyperinflationary fiat backed by nothing but the word of the Zimbabwean government saying how much it's worth. An inflationary currency can depreciate close to zero. But a deflationary currency's value can only go up. Which currency would you rather be holding?