If the number of people using the coin increases (demand goes up to match that), then the same percentage of coins (or even less) can make you richer .. you got more of something that's worth the same, or higher, in real terms.
Population is always increasing. Then there's timing effects. Money is a flow, not a stock, and inflation doesn't always happen evenly, and all at the same time, so prices changes don't always correlate perfectly with money supply changes. Too naive to say inflation doesn't make people rich, but it's easy for people to say it all the time. 2-3% inflation is making SOME people richer