its literally a market tactic to sell things in stack sizes that you do not want. making you under or over purchase things
See, for me, it's the reverse. As a seller, it's a pain in the ass to have to eat up multiple sale slots just to sell off stock in quantities people actually want. I'm not trying to rip people off; I just want to get rid of my crap.


Finally, if you only need a few items of a stack, you buy the stack and put the ones you don't need back on the market at the price you paid.
This is also a pain in the ass.