It is true that something of value can be hidden, mainly because it is meant to be protected from preying eyes. You simply cannot find something of value anywhere, anyhow, it is mostly kept, this is how it preserves its value.
Sometimes, a treasure can be right in front of you but you would not know because it is kept hidden to preserve its worth. You can imagine a treasure seen on the floor or a treasure that can be picked from a tree, it would not be called a treasure anymore since anyone can have access to it.