The issue is the "uniqueness" that is inherent in each piece of real-property
US Law recognizes that inherent uniqueness in many ways. (For example, the holding of a right and/or requirement of the parties in any real property contract to "specific performance" because no two real propeties are "equivelant".
Eminent Domain is supposed to be rarely invoked for this very reason. This widening the scope of eminent domain takes a little more power and wealth away from the individual property owner, and gives it to the government.