If they have a better option than their current one, why don't they take it?

Their second best option would typically pay less, meaning the workers would die off even faster.

There are many effects here, for start if food places start going bankrupt remaining ones can raise prices and pay some sensible wage.

And anyway, if getting unemployed means that you will die - then society has a large problems. (assuming country in XXI century, does not apply to historic situation where resources were not sufficient to feed everyone)