I can't speak for every country in the world, but I know of no impediment that an employer can use in Australia (where I'm from) to prevent someone from leaving, even if they have outstanding debts or obligations.

As far as I was aware, it was mainly the Gulf countries that prevent people from leaving without their sponsor's permission.

I'm also confused about the circumstances in which someone can leave without an exit permit. From what you're saying, someone without a contract and no debt can leave without permission. Does that extend to any foreign nationals other than those on tourist and visit visas? Or are you just saying that tourists can leave freely? (lucky them!)