If it wasn't obvious already, the worker ants do all the WORK in the ant colony. This means foraging for food, looking after the colony's young, and defending their home for unwanted intruders. One nest in South America has had up to 700,000 members, so as you can plainly see, worker ants are basically expendable.
The queen ant, on the other hand, has a unique job and therefore lives a significantly longer life than her workers. A queen of the species Lasius niger in Europe lived for 29 years in captivity! Queen ants lay all the eggs that grow into the colony's worker ants. A leafcutter ant queen in South America lived for 14 years and bred over 150 million worker ants in her lifetime!
(Sources: 1 2)