I mean they have a standing army more than a million strong. Each member of that army can wade into battle outnumbered 100:1 and still win. Not only that but they are IMMORTAL. Killing a guardian only pisses them off.
No worries your city is protected by millions of immortal juggernauts. With magical powers to boot.
English
#Destiny
-
Because The number of aliens out there probably outnumber Guardians by a margin far, FAR greater than 100:1, and also have more advanced resources (large ships with slipspace technology, for instance). Most of those Guardians are fighting battles, investigating, collecting valuable resources, and assassinating high value targets on a variety of planets, or training on designated crucible zones. The enemy is constantly at the gates. And the people in the city can only die once.