You don’t have to spend your savings on trinkets.

If a company wants to expand and build a new factory (say to provide more, cheaper pharmaceuticals to more people), it needs capital. If you have cash but there’s deflation, you might just keep your cash under your pillow because it’s worth more every year. If instead we have an inflation, and so you have a disincentive to leave the cash under your pillow, you invest it (give to that company to fund its factory). That’s good for society.