Because those are the most desirable places to live. Homeless people move too.

Granted, there are homeless people who have a stable life but work a job that just doesn't pay enough to afford a home, or people who are between jobs and are temporarily homeless. But those people generally sleep in a car, cause few problems, are largely invisible, have most of their needs met in some way, and are generally not the people we are concerned about when talking about "the homeless".

The Homeless™ usually have more complex issues like untreated psychological issues, drug problems, etc. And while the previous group would rejoice about small cheap housing, it does little to solve the issues of The Homeless™.

Most expensive homes yes, but that doesn't mean there aren't plenty of livable homes and apartments that are _empty_ at any given time. Canada has a lot of vacant houses.