I know this is a bold statement, but here is why. Since the launch of Final Fantasy XV on mobile, Machine Zone has been slowly moving gameplay rules from FFXV to its other two big titles, Game of War, and Mobile Strike. To buy shields in FFXV you need loyalty points, and they can only be bought in an alliance store.
Game of War just removed the ability to use your massive amounts of purchased gold to buy shields and changed it to purchase with loyalty points only. For the uninformed, loyalty points can only be earned at the time, through alliance quests etc. and can not be purchased with gold or real currency.
Mobile Strike is usually a day or so behind on these changes, so if you play Mobile Strike, stock up on those 30 day shields before you can’t. Let your fellow players know.