Item Shop Item Rotation?

I from time to time surf the Item Shop even though I havent bought anything from it, apart from spending some of the temporary promotional 200 Cabal Cash(now eCoin) the put in after they transfered over to estsoft. I might buy something from the Item Shop in the future, but I like many who play this game, if I wanted to purchase something from the Item Shop, I would have to wait for the items in the Item Shop to be rotated untill the item I wanted to purchase was availabe in the shop. I've always wondered why they couldn't just put all their eCoin items in the Item Shop at the same time(do away with rotating items) and make all the items available 24/7(aside from any holiday/special items if the are any) like the way Rumble fighter does with their Item Shop.

Hmmmm...no posts? I hoped that someone else would be interested enough in this subject that they would comment on it. I wanted to know why they feel any need to rotate the items in the item shop.