Some historical context:
A long time ago, many many updates in the past, in the original external beta version of the game (version 0.34) there were universal Glyphs.
In the first update, 0.35, these universal Glyphs were segmented into the colored Glyphs we all know today.
Patch notes:
Side note: This replaced the original evolution system of Fluxes, which required the player to farm 3 additional copies of the thing they wanted to evolve to the next rarity and sacrifice them with the Glyph and the appropriate tier Flux (which were only available in the Quest Pass at the time, so there was no Legendary or Mythic evolutions without a Quest Pass purchase).
Hindsight commentary: Fluxes were publicly said to be scrapped because keeping duplicates of things for potential future evolution was too much of a burden on inventory space. In a game world today with Northelm inventory upgrades post level 50, this system could have been workable today. 