Crafting is probably the best way to both make and lose money in this game. The desynth materia goes for hundreds of thousands of gil and Crafters are needed in order to make vanity and housing items. In addition, in order to meld materia into a piece of gear you need to have the required level with the gears associated crafting origin. In a sense, without crafting you cannot effectively farm for expensive Grade IV materia or put up items for sale that go beyond base materials. Not to mention that the crafting mini-game takes a bit of skill to master and be quite entertaining if you're actively trying to make HQ products.

So if you simply want to do dungeons and not mess around with Vanity for your character, make millions of gold, create unique housing items, or invest into what SE may inevitably bring out for crafters in terms of end-game gear, then it's probably not for you.