Why Armor?

Just a quick thought--Why do the characters wear armor? If their Jaeger is heavily damaged and the pilots are exposed, they would have little chance to defend themselves from any of the monsters, even in an armored suit. Maybe the armor is integral to how the Jaegers are piloted. Maybe they'll function as space suits/pressure suits. But then you have to wonder how a monster might propel itself high enough into the atmosphere to warrant the need for humans to have such a suit.