Quite simply it is a cost option.
You have a gun with useless barrels so you cant sell it or use it. Your options in order of expense:
You can re-barrel it in England.
You can re-barrel it in Spain or Italy.
You can sleeve it to the best possible standards and have a proper barrel maker strike it up like a pair of new barrels and TIG weld the join to make it invisible.
You can sleeve it to average standard.
You can sleeve it cheaply.
Whatever choice you make will affect the outcome and the subsequent value of the gun.
