Inflation makes "saving", in the sense of stuffing your money under your mattress, less appealing than "saving" a.k.a. "investing" by putting your money into other enterprises in the hope of an above-zero return. The former removes value from the economy, and the latter adds value, so incentivising it that way round is a Good Thing.

Notice that inflation does not "steal" any value from savings that are not money: property, for instance, or art. It encourages the ownership, and thus production, of things that are real things, and not things that are just money. How is the opposite of this desirable?

Peter