You don't really need guild marks until later anyways, why would you hoard them before you even start using them?

Besides, you don't really need any of what they give you for 'em. Maybe if you could trade in an obscene amount of guild marks for special gear related to that class *COUGHSEPLEASECOUGH* or DoH could trade them in for rare mats *COUGHDYESCOUGH* but otherwise they're not even very useful.