Because of how the trials are designed, and how unproductive Walk of Echoes can be now, it's often easier to just make an Empyrean weapon that will be left at 85-90 for a very long period of time than to make the "easier" version. Plus, unlike the level 99 version of the lesser weapon, the lower level Empyrean has room for growth if a number of someone's loved ones die and his or her FFXI playtime then increases.
This will probably change if Coins of Lack of Advancement Because they're Always Coins of Ruin can ever be sold over auction or bazaar, which has been mentioned as a strong possibility by a Development Bro if I'm remembering correctly.
