poor

Because nobody gives a shit. The city doesn't, the landlord/property management company definitely don't. If you're below a certain income in Canada, you're considered subhuman and unworthy of protection.

Even if the government cares, poor people still don't have the time, energy, or money to fight stuff using the law. That is very much a privilege that comes with wealth. Filing formal complaints with the government, or a lawsuit, takes ages and requires a ton of research to do correctly. And it's not like they can just take a few weeks time off from their shit paying job or afford a lawyer to do it for them. Not to mention the court/filing fees.

Finally, it's not unlikely that even if the city cracks down, instead of the landlord actually fixing the issues, they'll just shut down the building and displace all the people living in it, because the government can't force them to provide housing and also have no interest in turning it into government-owned public housing, so if it gets too expensive for the landlord, they'll just sell it off probably to a luxury condo developer and there's nothing the tenants can do. Having a shitty home is still better than having no home so it's not a risk that people who can already barely afford the shittiest housing want to take.