The problem with overstrikes is that they are unattractive looking. Most collectors like their coins as unspoilt as they can get them. It's only those who are interested in financial history who appreciate overstrikes for what they are: testimony of shocking coin reform, political instability, wars, rebellion and other misfortune. By understanding both host and overstrike, you have a record of turbulence, that would not have been there if there had been time for orderly re-melting. However, students of financial history don't need actual possession of the overstrike. All they need is a solid source of information of its existence. That leaves only specialists interested...
Peter