[specialist]

Yes and:

Emphatically agree with you.

Substance abuse contributes to homelessness AND homelessness contributes to substance abuse. It's a downward spiral.

(When living rough, a lot of people turn to self medication. Someone already suffering (eg chronic pain) loses access to proper meds will then use whatever's available. Etc.)

Expecting people to be clean and sober before getting housing is imposing inappropriate morals and standards onto an already terrible situation.