The other side of your argument: The difference between inflationary risk (your argument) and market risk (my argument) is not insignificant. We already have a substantial B fund that is subject to both market risk and inflationary risk. The A fund does not currently subject a large part of our retirement to market risk. Some of us appreciate that a lot.
Think global economic downturn, war in either Asia or Europe, or another adulteration of the market via some "creative" banking products traded by high speed computers. You lose half or more of the value of your B fund for some period of time, perhaps when you retire, or need that expensive healthcare that your insurance carrier won't fully fund. It should would be nice to have a guaranteed A fund pay out.