There are a few reasons inflation isn't talked about that much, but most reside in the simple fact that no one really notices or cares about a 1%-2% increase in average prices. At that level, it's hard to track the prices.
Let's take cereal. Right now, a 8.9 oz box of Cheerios costs $3.19 at my local Meijer. If that goes up 2%, that's just $0.06 extra per box. Plus, I'm probably comparing prices and using coupons, so my actual cost might be $2.50.
It would take over a decade at 2% inflation for my sale/coupon price to reach the normal price, and we really don't pay attention to small price changes in the long term. We even ignore the aggregate grocery bill, as we tend to just chalk it up to overspending now and again, not price increases eating away at our budget.
Inflation only gets talked about when we see rapid price changes, such as housing and lumber a while back, and now damn near everything.
Also, you're right about a federal wage of $20 having disparate effects across the country, but we already have a federal minimum wage, and it's depressing living standards in the higher cost areas, the opposite of your concern with the $20 level.
The cost of living adjustment is difficult, but it might just be a more permanent solution to our problem (unintentional reference to Jesus Christ Superstar).
One option could be leaving it to the states to decide, but then you have states like Illinois, where $20 is great in the rural communities but goes nowhere in Chicago.