They don't because SE in all it's wisdom decided to just cordon off crafting from anything meaningful. Raiders may insist on sucking the fun out of their content, but crafters also do that, just they have to deal with RNGesus more.
Honestly, I don't think Minecraft/Terraria is even good at what they do, they're just RPG games where the crafting is placed in an easily accessible manner, and the combat is narrowed down to "press X to win", a real MMORPG based on this concept would never actually work, since the botters would just rip up the world, and the game would be dead within days. Plenty of MMORPG's have pseudo-sandbox crafting/resource management, but ultimately they're just unlimited resources, and thus subject to unlimited supply and scarce demand (Landmark (Everquest Next) actually did this, and it just kinda felt like "pretty minecraft" and little else.)
If FFXIV was designed around crafting being the only way to gear up, instead of winning tokens/tomes from dungeons, we would be getting a single drop of (RARE ITEM TO MAKE GREAT GEAR), and people would moan and complain about the RNG aspect of it MAYBE being a drop like it would in most other RPG's. Then you also risk destroying the item in trying to craft GREAT GEAR. The stress in crafting isn't the "crafting" but trying to get the materials in the first place, and if content keeps moving along at a pace that you can never manage to keep up with, then you'll never be able to buy those items and instead will have to hunt them yourself, thus taking time away from the part of the game you enjoy to do the frustrating part of the game.
Like there is really a formula for this, and SE just doesn't use it. Raiders seek out the rare crafting loot stuff and sell it to crafters, crafters turn around make gear and sell it to raiders, gil sloshes around between the raiders and the crafters, and sinks when raiders no longer want to do that content or crafters can't find any profit in making those items. That's why the tomes exist, so the content can still be played, even if there's no crafted gear. But in doing so, there is no incentive to even bother with the crafted gear, so crafters instead get told to do daily quests for scrips... which is their own version of tomes.
In some ways I feel that the developers just kinda forgot about crafting in FFXIV entirely. In other games, crafting the GREAT GEAR would involve things dropped from multiple pieces of content so one player could rarely make it themselves (or at least not without multiple characters since most other games don't let you change jobs.) However in practice, people just find challenge in doing content solo, and the game doesn't really incentivize you to play hard content, which is where these rare drops are supposed to exist. Even the entire "Mythic+" type of idea would hinge on there being some incentive, and if you say did M+ and got that RARE ITEM TO MAKE GEAR GREAT AGAIN, you would need it to craft the gear (or craft the key item to progress) to do the next level, or something to that idea. But knowing SE, we'd just get M+ tomes and nothing would change, and there would be no reason to ever play content cleared, just like now.