I know this is of topic, but I feel needs said.
The items that are in most demand are so because they are the most difficult to get.
This is a good thing, it creates high demand which means they have higher coin value, meaning people want to sell as well as buy, and as people value coin it makes a reason for some to gather.
So it’s actually a good thing.
If everything was easy to get, or if mats were used in recipes only in quantities that match their abundance, then everything becomes the same, and everything has the same value, and lack of variety would be a big issue (it already is a bit of an issue currently).
Edit: BTW, I don’t think harvesting glow caps is the most efficient way of getting shims! Have a little look in your knowledge tab and you might find a way to increase the amount of shims you gather!