If you look at the vanguard class emblem, it's almost like it's missing something.
It has the titan, warlock, and hunter class emblems on them and then a 4th, almost just...space wasted slot.
Is Bungie just being lazy? Probably.
Perhaps it's just insurance in case the team decides to throw in a 4th class.
I like to think maybe they got something random in the back of their minds.
Food for thought...
Maybe having the ‘blank’ part covered with stripes represents what we’re fighting for in an all-encompassing way
Like the US flag has 13 stripes for the original 13 colonies. It could represent the various habitable planets that were colonized during the golden age.
Maybe philosophical tenets they abide by. Maybe the citizenry. Stuff like that