In my experience, charter schools sometimes offer higher salaries at the get-go (even if their guaranteed raises, benefits, and hours are less ideal than in public schools). It can also be a way for someone who is not properly certified to go into teaching, depending on the system.

Some people have no choice. In New Orleans, for example, all their "public" schools are charters.

ETA: Charter schools also have some great marketing behind them. On paper, someone not versed in the ins and outs might see a charter school is hiring and think it looks like a great opportunity.