The problem with glamour log is most likely how the item/gear data is saved because the inventory system was not designed with glamour log in mind. That means the glamour data is probably attached to the base item data, which means that just getting glamour data comes with a large amount of unneeded parameters for all the other values the item has. That results in massive amounts of unnecessary data being moved around, just to get to that one part designating appearance, which in turn results in the glamour log not being a feasible option at the moment.

Changing a core system that the whole game is built on basically requires redesigning the whole thing, and that takes time and resources. It's like trying to change the foundation of a house after the house is already built, you don't just take it out, in the case of FFXIV the house is more like a skyscraper too. All the other systems depend on the foundation so it's not easy to change it.

If a glamour log was suggested 7 years ago when they started making the core item system, I'm sure we could have it, but since that wasn't relevant at the time, the current core system is not flexible enough for it.