A former trustee in the inner-ring suburb in which I live owns and manages rental housing throughout the municipality and is a vocal opponent of building new housing, and of the argument that supply and demand functions in the housing market. I could screenshot him for you, but you have no idea who he is, so: just take my word for it, these aren't "alleged" people. They're a major force in local politics around the country, which is where this fight is primarily being fought.

For the same reason that NIMBYs care so much about urban trees or spotted owls. They don't actually give a shit about them, they just are willing to say or do anything to sabotage the process of increasing housing supply.