Might have to do with either (a) the troops you deem “valuable” for traiting, relative to the total; or (b) the discrepancy between troops released on Console vs. PC; or (c) your home kingdom and those of the teams you invade.
Its that low? Those 2,200 gold keys each week for a year sounds good now
(a) I Trait everything I can. Currently I have over 80% of all Traits and I have every non-Arcane Trait
(b) This must be it
(c) Traitstones drop randomly in Console PvP
Looking at the yellow and red traitstones Rasper still requires it seems home kingdom hasnt had much of an impact…