It was recently pointed out to me that health insurance costs roughly the same to purchase for each employee, so with wildly different wages, the percentage that health insurance makes up of the total cost associated with an employee also differs wildly. So while health insurance might make up e.g. 5% of what is paid for a software engineer, it could make up 80% of what is paid for a janitor. This puts a big incentive on companies to get rid of their lowest paid employees (or wiggle their way out of providing benefits), since there is essentially a fixed price income tax that always needs to be paid on any salary regardless of it's size otherwise.