I fully agree that the new endgame content should be able to stand on its own. But I've also seen many posts from people who feel like they can't get their hands on enough Etheric Light. They, for whatever reason, simply can't gather it in the quantities that some players do. This idea allows them another avenue to grab another few using marks that aren't being used for anything else. It would also give players who didn't purchase HoW another way to acquire this material. Players hated, I mean DESPISED, farming for planetary materials so Bungie implemented a marks for mats exchange. Farming those materials was a very simplistic task that anyone could do but players hated it with a passion because it was mind numbingly boring. Etheric Light can't even be farmed easily unless you can gather a group of players to take on PoE or ToO. It's much harder to acquire than planetary materials, which would imply that an exchange would suit this material very well. Lastly, you know as well as I do that the bad content in this game, cough cough crucible cough cough, gets plenty of repeat visits because the sheer number of players in this game makes this possible. I'm simply creating another avenue for Etheric Light to be used by players to help if they've had a bad week in PoE or ToO or just to supplement the poor bastards like me who didn't/won't buy the DLCs.