The problem is that there are a decent amount of extremely wealthy people who absolutely do not get anywhere near 1.5 M in yearly "income". Many of these folks

The problem is that there are a decent amount of extremely wealthy people who absolutely do not get anywhere near 1.5 M in yearly "income". Many of these folks live off of things like dividends, capital gains, or even better loans against ever rising investment portfolio amounts (with the added advantage that the interest on the loan is tax deductible). The emphasis of the tax code on "income" per se, which does make sense on several levels to be fair, ends up missing a significant portion of very wealthy folks who just don't have much "income".