I gave a very rough explanation of my thoughts which was my fault. My original meaning was focused mainly on Crafting gear and was meant to focus on the difficulty of obtaining high-end Crafting gear translating into omni-crafting being much more difficult to do, allowing (Or rather forcing) most people to take their time gearing out their classes and needing to rely on others for a longer period of time because they won't be able to craft everything themselves for some time. In this way omni-crafting takes longer to achieve, adding a much needed length to Crafting's Endgame for those who enjoy it and the benefit of an active market for a longer period of time.
Crafted Combat gear is a whole other issue by itself, the primary reason you don't see any being that the majority of them can be beaten by gear you can get in a day or week and not worth the millions of gil it currently takes to Craft them. That, along with the decreased impact of secondary stats and limited availability of Favor items/Tokens makes crafting any of the pieces a gamble at best, since there is no guarantee anyone will buy the item, especially considering the cost.