From what I've seen, it's more likely that it's because it's easier and cheaper to building housing in Nevada than in California. The states where homelessness has improved are generally business-friendly and low-regulation states.
More like they'll take the path of least resistance and go to the next town.
I'd love to see the data to back this up. Sounds like you're coming from some idea that most homeless want to be lazy and not work and stay homeless, and if jail were threatened, that all of the sudden they'd get a job and re-integrate into society. That's extremely disconnected from reality.