I'd kinda prefer that the quests didn't reward gear, but that may be an antiquated way of thinking. The markets would be more active if players had to keep their armor up to date from buying from crafters.

Once you have one class leveled up there's a good chance the gear you accumulated from questing will carry over to another class, (if you choose to keep it) pretty much invalidating the reason to buy any gear from the markets. That and there's dungeon drops that you can stockpile for future classes you may choose to level.

The only classes that really benefit from the markets/vendors are crafters and gatherers since you only get one piece of equipment per 5 levels from quests and you only can get 1 tool and 1 piece of gear from that.