Many people have a warped perception of what it is to be "homeless" or, more generally, "housing insecure". There are stages.
The first stage is where you're staying with friends and family for variable periods. Couchsurfing, attics, garages that sort of thing. You probably still work but can't afford the security deposit and first and last months rent. Maybe you can't even afford rent. You probably lost your house because of a relationship breakup, an eviction from income disruption, etc.
Stage two is where those options are exhausted and you're living in your car. You are probably still employed. Sometimes you may park that car with someone you know but as time goes on you'll be parking in parking lots and on the streets. You may suffer break ins, run-ins with the law, etc. At some point that car will break down and you will lose your job because of it. The car is staying where it is until the city impounds it.
Stage three is the first stage people notice. You're living on the street because you've lost your car. In places like NYC the homeless may seek shelter at night on the Subway. This leads to a lot of "homelessness crimes" like loitering, turnstile jumping and traspassing.
Stage four is where this life has taken its toll. You probably have mental health issues, drug dependency issues (initially from self-medication), etc.
So stage three is where many think homelessness starts. They may still be able to work but this becomees increasingly difficult without access to a car and a permanent address. You might even use a Planet Fitness or YMCA to keep clean still. But housing security began long before someone gets to this point.
And in all but the last stage, simply giving someone housing will solve their problems most of the time. As time goes on you may require other intervention such as mental health treatment, social work and treatment for substance abuse.
But unfortunately a lot of this gets criminalized, which both costs money and makes it more difficult for someone to recover, having a criminal record.
We live in a world where we'd rather spend a lot of money militarizing people to harass homeless people and on prisons to house them when we can spend a whole lot less just giving people somewhere to live.