just to clarify.... aren't the cartel market certificates both BoL and stackable? I realize it went through a few iterations to make it that way (they were first stackable and BoP, then they were BoL and not stackable, but now they're BoL and stackable)
I'm ultimately indifferent either way. I think the current implementation is fine especially since the things you buy are BoL, but I guess I just wanted to point out that not all items fit those 3 descriptions.
My guess is because the helix components pre-date the Cartel certificates and they'd have to do a massive overhaul to the Gree system to change them and decided that it wasn't worth it.