Because being homeless does not mean that you are suffering from mental issues. It's also much harder to address the real problem of not addressing mental health, when you lump it all into the same category of homelessness.
I know it first hand because I used to be homeless (but not "visible homeless") at one point.
> Because being homeless does not mean that you are suffering from mental issues.
A relevant part of them do, or we wouldn't have this discussion. That all sounds like "we have good help systems for some homeless" at most, which then somehow gets generalized into "we have good help systems for homeless" when this obviously isn't the case for a part of them.
I know it first hand because I used to be homeless (but not "visible homeless") at one point.