Mainly for use with ghost's inventory system. Let's say you have 3 printers. They would all occupy the same slot, but you would still have 3 printers there.

And it would be nice to have compatibility with the inventory system.
You would be able to control the max stack like this:
(maxstacks.txt in add-on.zip)
gunItem 10
printerItem 50
spearItem -1
-1 would be infinite stack. Or at least the maximum the inventory system can handle without flooding the screen with "999999999999999999999999" or something. 0 will just be changed to 1.
I'm sure if you played minecraft or terraria or RPGs with a grid inventory system you would figure this out.