Why so many travel positions?

I want to move out of the state of Florida to California. I have my resume ob Monster & CareerBuilder. I get lots of phone calls from nurse travel companies that only have 13 week assignments. I need a stable, permanent job that will pay for relocation & benefits. Seems like unless I want to work in Savannah, Ga or some other state that I would never live in, relocation & permanent work isn't going to happen. Why have so many travel positions if nurses are needed this bad?
Sadly many hospitals rather pay for travelers than pay for benefits/other expenses that come along when employing FT/PT.
All medical staff should have life time health care. We are exposed to everything. I think staffing companies have there place, but we are at risk as a profession. I hate to use union busting as an example, but it is the same. We have no protection.
Most of the companies that offer these travel positions do offer health insurance. However, no other benefits like vacation & 401k.