Because that's when they'll get upset and use all their connections and money (which they also have) to fight that tax. Worst thing that can happen to them is t

Because that's when they'll get upset and use all their connections and money (which they also have) to fight that tax. Worst thing that can happen to them is that they need to feign defeat in some income tax hike battle as a pawn sacrifice to pull more non-owners on the "taxes are theft" side that protects them. Add to that the practical problems of land ownership tax (how do you assess something that hasn't been on the market in decades or even centuries?) which make it easy play the "why not tax something that is easier to tax" game. Historically, the solution has been violent upheaval every couple of generations. A nonviolent alternative might be an occasional "inverse bankruptcy" lottery or poll cutting off randomly selected and/or particularly unpopular tall poppies. With the right dosage (not too often to not stifle ambition, perhaps aiming for hitting one in ten outliers in their lifetime?). The goal would be to prevent concentration approaching the infinite, not to make people equal (and the victims could still receive a very generous stipend, or wouldn't have to be hard on them at all, at least in day to day material terms)