Janitors. Nobody thinks about them or appreciates what they do. But you can be sure that if they all disappeared, people would suddenly realize how much we depend on them.
Public defender. Getting paid low, having to work incredible amounts of hours, and having to defend people you don’t want to defend.
Water treatment workers, Heating, Ventilation and Air Conditioning (HVAC) technicians. The number of people who couldn’t survive without clean water & heating/cooling is staggering.