This is a charge to the site holder for the value of the site he occupies. This value is provided by the community surrounding the site - the site holder in no way raises the value. His community made his land valuable, so it seems fair for the community to recapture the value it created. Much more important than revenue, however, are the economic consequences of collecting Rent. The overwhelming problem from one end of the earth to the other is land tenure and land speculation.
Land speculation keeps land off the market.
The land market can be likened to a collectible market. Just as a Renoir is not for enjoying, but for holding for an anticipated increase in it's sale price, so is land. The economic consequence of this are seen in every major city in the country. Unused and under used land abounds. Structures are boarded up, empty, except for the homeless who force entry.