I agree with Dan. The USPS mission statement defines its basic functions...
Quote:
The Postal Service shall have as its basic function the obligation to provide postal services to bind the Nation together through the personal, educational, literary, and business correspondence of the people.
Stamp collecting is not mentioned as a core function and is simply a collateral profit center for the USPS. I assume that the vast majority of taxpayers, who are not stamp collectors, would rather the USPS be use efficient cost saving procedures and use safeguards that prevent reuse.
Although my experience is limited to my own local delivery, it seems that older stamp more frequently get pen cancelled. It may be that they cause humans to get involved rather than stay purely in the automated mail stream.
Don