Why do we assume that players who choose combat skills over economic skills should be able to make lots of money?
This isn't an anti-fighter question or a pro-crafter question. It's about gameplay balance. MMOGs tend to have some skills that are obviously intended to allow characters to make money, and some skills that are obviously about defeating players/NPCs/mobs in combat. So why should anyone think that those who specialize in combat skills ought to be able to make lots of money by killing mobs?
Letting master combatants amass towering piles of cash by defeating enemies through strength of arms makes no more sense than letting a master merchant buy a high military rank or an advanced weapon certification. We don't let economic abilities translate to a high combat rating -- why do we let combat abilities translate to a high economic rating?
Fighters get a number of unique rewards from using their combat skills: combat XP, weapon XP, weapon certifications, military rank titles, interesting loot items (sometimes), and the thrill of the kill. Crafters get different rewards from using their economic skills: money, and the satisfaction that comes from creating things.
So why should fighters expect to get economic rewards in addition to the rewards they already get from combat activities?
Crafting offers only a couple of rewards. Giving fighters access to one of the few crafting rewards in addition to the numerous rewards that combat already provides only reduces the perceived respect for crafting as a valued playstyle. Crafters provide unique services to a game world. They should retain unique rewards.
Fighters ought to be poor but deadly, and non-fighters ought to be weak but wealthy. This creates opportunities for useful interactions between both types of players -- crafters should need fighters to protect them, and fighters should need crafters to give them jobs to do to make money. This would mean that fighters wouldn't be able to buy that great armor or superweapon the first week they start playing a MMORPG because they ground out a bunch of high-paying quests. It would also mean that crafters wouldn't be able to obtain resources or valuable items without the help of capable fighters. Players would benefit from working together to help each other do better over time.
Basically, if you want to make money, spend your skill points on crafting/economic skills. If you want to be able to defend yourself physically in PvE or PvP, spend your skill points on fighting skills. Don't expect to be able to make a lot of money or be safe from physical challenge if you aren't willing to pay for the skills that allow you to do so.
In short, no one player style should provide access to all player rewards. Ultimately, that leads to the worst sin any game can commit: being boring.