When you put an item in an anvil (provided you have enough experience) you can re-name that item. Usually this is used for nametags and equipment, but can be used for anything.
I recently used this to name a stone brick block (for bit of fun), but when I placed it down, the name was not visible. I picked it back up again, and it still had the same name, so why is it not showing when I place it down?
Normal blocks (such as stone, dirt, etc.) do not contain tile-entity data. Blocks with tile-entity data (such as chests, banners, signs, and other blocks with inventories) can store their names in their entity data, but normal blocks do not have this extra data and as such have no name to render, have no entity to render a name, and have nothing to retrieve a name from when broken and dropped as an item.
So to clarify - you can name any item in your inventory, but any normal block that is then placed after being re-named will lose that data, and revert back to it's original item name, unless it is placed in an item frame.
Because it is not an entity. It can not have a visible nametag. It must be a mob, or an item in an item frame.
