what decides which items have limited stock and some just in the store? asking mainly bc some items that are high demand but are rarely ever sold on market don't seem to get restocked which i don't get the point of. item in question being the shin guards

Hi, let me take a look into that for you. Sit tight.

Some items are just limited, that's about it. Can be seasonal items like Halloween or Christmas stuff, can be just items we intend to be somewhat exclusive and thus only having a limited quantity available.
Shin guards were only available as an event reward and weren't being sold in Store.