A lot are also alcoholics and/or addicts - this is one of those things where saving money is the short term (not managing the homelessness problem before it got to this point) results in a higher cost in the long term - now you not only have to manage homelessness, you also hav to help the existing homeless recover from long term homelessness.
You also have the long term costs of assisting those with mental illness (as a result of "saving money" by closing down all state level support for mental illness in the 80s - I'm not saying that was a panacea, but having the support helped a lot of people that currently get no help).
Politicians love "saving tax payer money" through short term things like this, because they know that by the time someone has to fix their mess they've moved on/retired and they don't have to deal with it.
Although the people who fight housing seem to not grasp this.
[1] https://www.washingtonpost.com/business/economy/in-expensive...
Basically there’s no way you can “fight homelessness” and “fight apartments/evil gentrifying landlords”, and actually expect to do anything about homelessness.