Am I Missing Something?

(Via Daily Kos) Is there some reason why the minimum wage can't just be indexed for inflation? The latest proposal, from Rep. Steny Hoyner, proposes raising the wage gradually from $5.15 to $7.25. Which really just leads to another minimum wage fight down sometime down the road, right? This should be simple, just pick a number and index it for inflation. That way you only need to revisit the issue when you actually want to change the minimum wage, not just make up for purchasing power that has been eroded due to inflation. I'm metaphysically certain I'm not the first person to suggest this... is there any good reason why it hasn't been done?