It seems to me that if this rule became widespread there are two unintended consequences that come to mind:

1. If an aircraft has a statutory life of 15 years, then is has a value of $zero at the end of 15 years. If there is no residual value at year 15, this would have a major impact on airline balance sheets; raising operating costs significantly. There would have to be an increase in fares to offset this loss.

2. Giving the $zero residual value at 15 years, aircraft manufactures will (of necessity) begin to design aircraft with a life of 15 years. I'm not sure I want to ride on a ten year old plane that was designed to fall apart in 5 more years.