Power
The pay isn't the best, but the power to influence the minds of future adults is pretty awesome. It's not the same power as being a pirate or a dentist, but you're being trusted with the world's most precious commodity: children. True, your students won't really remember you or any of the carefully-planned activities you'll design, but you'll be a child's regular source of warmth, love, comfort, acceptance, and safety.
If you can teach a child to resolve conflicts, make decisions, form friendships, and follow instructions, you're making the world a better place. We think that's a lot more power than Iron Man has. Iron Man has to protect the world from people who didn't go to a good preschool.