I understand this, and smaller quantities are usually available but you'll typically pay a premium for them. Small quantities of base ingredients isnt cost effective though - whether you're a bulk crafter or not. Buying stacks low and churning the stock gradually is often significantly cheaper.
Take Dwarven Cotton which is used for a bunch of dwarven threads, mats and gear; and is also part of the BLM style glam sets. On my server a stack of 99 is nearly half the price compared to a stack of 20, and 1/4 of the average individual price.
It might be in part because they are used in a glam set, but they sell in large quantities and are a fairly stable market. You dont even need to HQ them. So, harvesting enough bolls for a few full stacks of bolls, threads and cloths and putting them as full stacks is worthwhile.
Lets say I harvest and craft 2 full stacks of bolls, threads and cloths, and a few gear set items. I can list the lot taking up 6 to 10 retainer slots and shift them quickly.
Or I could split the stacks into 20's taking up 20+ slots which while they will sell I would prefer to use for slower sellers that Im trying to shift. I would also be taking up 5 market board slots instead of 2 for each item which would potentially tank my own market - particularly if everyone followed suit.