Why the Colts and the Saints should try to go 16-0

Both of these teams should try to go 16-0 because they both have not lost a game this year and why lose one now when you do not need to. Actually I think they should play their starters even on the last game because then they have no chance to get rusty because they can not play. Also if anyone is injured then you can take them out. So if i am the Colts or Saints take a chance.