It seems like the left is already doing that, just in the opposite direction. Poverty has continued to decrease in the U.S. so we longer talk about it much, instead we focus on "income inequality" because it serves a particular political philosophy. If "income inequality" is a major issue regardless of how well people are doing, then there will always be a reason to intervene in the economy and redistribute wealth, since any society with any sort of market economy will always see an uneven distribution of wealth.