If the purchase of land becomes necessary within a designated wild and scenic river corridor, why would condemnation be used?

Should the purchase of land become necessary, condemnation is typically a last resort and only used when:

  1. Land is clearly needed to protect resource values, or provide necessary access for public recreational use, and a purchase price cannot be agreed upon.

  2. Clear title to a property is needed, in which case condemnation is merely a legal procedure that has nothing to do with government/landowner differences.
Source
Interagency Wild & Scenic Rivers Council