I thought the same, too. Generally some small amount of inflation is preferable to encourage spending, rather than deflation which discourages it.
If you know a $100 item will probably cost $102 later then you're more likely to buy it now. But if that item will cost $98 in a deflationary environment, then maybe you'll wait to buy it later. Wages also tend to fall in deflation, which makes it harder to pay back debt, so lending slows down - people won't buy houses or cars, etc. Businesses hold back on capital spending. The economy slows to a standstill: if no one is spending money, how can anyone make money?
If you know a $100 item will probably cost $102 later then you're more likely to buy it now. But if that item will cost $98 in a deflationary environment, then maybe you'll wait to buy it later. Wages also tend to fall in deflation, which makes it harder to pay back debt, so lending slows down - people won't buy houses or cars, etc. Businesses hold back on capital spending. The economy slows to a standstill: if no one is spending money, how can anyone make money?