Usually because those responsible for regulating housing are heavily invested in it, and like the fact that high immigration is pushing prices up. In the case of more blatantly malicious governments, it can also be used to encourage divisionism, or to weaken the power of the working class. At best, its just because building housing (esspecially in more extreme climates) is slow and expensive. As usual, most things lead back to corrupt governments and capitalism.
At the same time, the goal of dark patterns to to make people spend more money. Given that revenue is very likely one of the key things Google wants (and thus promotes) out of apps, its also entirely expected that the apps people find are largely those who try and get the most money from users, which requires dark patterns.