They aren't philanthropists, they are greedy bastards, but they also aren't much different from people who buy stuff on MB fore resale.
I am judging it from the perspective of a person who wants to buy a house. If there is one plot and three players who are going to buy it, one being the player who can't get to the plot it time, one being the greedy bastard and one being a cute little miqote girl who wants to start her own flower garden, it's better if the greedy bastard buys it because then the player is able to buy the plot from them. Now I know that it is heart crushing that the little girl got beaten to it by the greedy bastard, but it leaves the plot open for whoever is willing to put in the effort to pay the greedy bill. It ain't nice, yet it's capitalism.
You are right, the system is broken. That's where I see the core of the problem, not the greedy sellers, but with the way the system is implemented. It's mind-blowing how difficult it is to add more housing in this game...
It would be nice if everyone could get a house, but I am afraid that such a thing would come at cost of making the housing entirely instanced on house by house basis... I am not sure many players would like such a thing. I have few friends who totally hate the idea and once the housing is freely available in instances they lose any interest in it. So I wouldn't be surprised if a noticeable part of the demand for housing came from it's limited availability.