It would help to at least try doing that, but in practice this would probably be very difficult - it’s likely not possible to always drink boiled water and well-cooked food, and given the possibility of contaminating food and drink after boiling, you might effectively have prepare all your drink and food yourself, which is logistically difficult given the length of the work days. Diseases also spread in other ways, like smear infections (e.g. on toilets, doorhandles, tools) and airborne infections.