I'm in a GQ focused guild but it's really hard to motivate people to do GQ when what's avaialble in guild market isn't very good.
You can only get one of the one and only building, then you have buffs and "smaller" adventures that explorers bring for nothing..... Why buy when you are in a guild and higher lvl members are more than willing to share?
It's not a very attractive shop, is it? No Fairytale or 1001 nights adventures? No hard to get stuff, especially not for players of lvl 55 and higher.