After a fresh server wipe you can find plenty of yellow protective cases lying around. A a few weeks later, some objects like these seem much harder to find (if you can find them at all...) It looks like there's a hard limit on servers and when hoarders in bases got them all, they won't spawn anymore.
I don't build bases (I’d rather destroy them), but I do like to make (and use) some improvised explosives :) Unfortunately I can't do that if I can't find all the required items to craft them.
Perhaps it would be a good idea to reconsider whether the hard limit for protective cases is still needed, because nowadays you can also use them for other things then just storing items.