Unlike in WoW, crafting disciplines largely don't provide perks you can't get any other way. For the most part, weapons, armour and consumables have account-bound versions that are slightly better than what's available on the trading post. (Notably, jewelcrafting is the odd one out here.) The big exceptions are legendary components: depending on which legendary you decide to make, you'll likely need to level a crafting profession that makes useful weapons for your class and one that doesn't have a whole lot to do with your class.
For completeness' sake:
Each crafting discipline can craft account-bound Gifts at level 400, used in crafting Pact Tyria legendary weapons. Each Legendary weapon needs a weapon-specific Gift, of which only the Gift of Lightning (for Bolt) is crafted by a weapon profession. These Gifts require a material gift, either Wood, Metal or Energy, which is crafted by the discipline capable of making that weapon, either Huntsman, Weaponsmith, or Artificer, respectively. Legendaries are complicated and expensive, so once you've settled on a favourite weapon, look up the legendary for that weapon.
Ascended equipment are account-bound equipment items that are technically best-in-slot for a profession. They are significantly more expensive than exotic-tier items for a very modest increase in stats, but ascended items can hold agony resistance infusions, which let you survive higher scales of the Fractal of the Mists. Weapon and armor crafting disciplines allow you to craft ascended equipment (note: jewelcrafters cannot craft ascended equipment, unless Heart of Thorns changes this).
Zephyrite Desert Recipes
The following food items are account bound, and can only be acquired by having a level 400 chef and acquiring the recipe from Zephyrites in Dry Top:
- Candy Cactus Cornbread
- Prickly Pear Sorbet
- Prickly Pear Pie
- Stuffed Nopales
- Cactus Soup
- Nopalitos Saute
- Roasted Cactus
- Black Pepper Cactus Salad
- Sweet and Spicy Beans
- Cactus Fruit Salad
Weapon and armor disciplines can craft some max-level items with unique skins. They can also craft Celestial, Nomad's, Sinister and Zealot's stat combinations, which are all account-bound. They also craft consumable items (stones, oils and crystals), of which some account-bound variations exist.
I include this because daily cooldowns are the 'perk' of many WoW crafting professions. Most disciplines get access to a few recipes that have a daily cooldown. Most of these recipes are somewhat cheaper to craft than to buy on the trading post thanks to the cooldown, with the notable exception of elonian leather and spiritwood planks. In particular, bolts of damask are significantly cheaper to craft than to buy on the TP.