Since it is rather tough to make a plane bomb-proof and missile-proof, I suspect that everyone just decided that new construction tricks would be fruitless.
Ten years. By now every 747 could have been retrofitted to fix the supposed cause of the explosion.
Note that the article does NOT say that ANY 747s hsve been retrofitted.
The article says nothing concrete about what specifically is done differently in new construction.
Since it is rather tough to make a plane bomb-proof and missile-proof, I suspect that everyone just decided that new construction tricks would be fruitless.