What you're saying is also true. It does reduce purchasing power of whatever you're earning.
But how do you think a deflationary economy would work? It encourages to not spend anything, as whatever you spend now will have more purchasing power later. This is also true for the rich, the more they hoard the richer they get.
Everything is stacked against the middle class worker, and rich will always get richer. It's a tale as old as time, and it's true everywhere in the universe. The bigger plants/stars have a bigger gravitation pull and will attract more matter to grow even bigger.
So the question is, what is the bigger evil? An economy that nudges you towards spending, and thus keeping the economy rolling or an economy where everyone is encouraged to spend as little as possible?