Quote Originally Posted by Iscah View Post
Sun, moon and stars are the three "big" things to draw on for celestial-themed symbolism, unless you want to include a generic planet in there as well – though the game avoids addressing whether there are other planets in the local solar system, so they probably wouldn't go for that particular one.
Yeah, there's not really lore about the seals per se, because they were added to AST after Heavensward when almost all its lore was written. The intention is pretty clearly 'this is the stuff that's in the sky that astrologians would divine by', though.

If I'm pressed to come up with a reason, it's probably like Moose said, a parallel to the signs used in astrology calculations. Or maybe the fact that it's always consistent means it's something more akin to the elements of astrological signs; the Balance just is a solar card, just like Cancer is a water sign.