I think it's petty cool to roleplaying smithy but problem is too grinding and too limited reward (I wasn't talk about money, it's just quest/order offer mere tiny gold, not beyond than that. Smithy should be very good profit, but downside, you too busy working on smith rather than battle, more or less, Smith is always useful to army, it's core to keep all weapon and armor in good health and even design better than normal, so I am glad it's part of game, but there is no craft of arrow/bow/armor, even horse armor to make custom looking, and personal touch. But Biggest problem is just too grinding and rest lot of to level up to get what you want, and too many locked, and unlocked weapon random, it's take forever if playing normal game without cheat/mod that allowed to unlock all items, even then, rest then craft, then rest, then craft, buy lot of wood and iron again and again, it's not fun. Should smithy part of game, oh yes, but should be lot of grinding? No, no way.
While Smithing should be very profit, it's second since everything other can be profit too, trade, raiding, loot, quest's paycheck, so go on but real a main reason is personal craft your own looking/damage/speed weapon/armors, and role playing in medieval age.