Whether or not people are in subsistence poverty is not the only measure of a functioning society. It's great that extreme poverty is going down, but let's not declare Mission Accomplished just yet. The existence of billionaires might not affect your running water, but it does distort the market and negatively affect how much everything around you costs, from housing to healthcare to groceries. The existence of billionaires also affects your share of power in democracy. A billionaire is right now, running amok, griefing workers and tearing down institutions. All because his billions bought him the power to do that.

You might change your "billionaires existing doesn't bother me" Enlightened Apathy if they one day kill a government service you rely on or decide your job must end because they need double digit stock growth again this year.