Why are no templates designed specifically for Facebook Video recommended aspect ratio 4:5?

Hey guys, newbie here!
I am creating videos for Facebook adverts. All of the premier video template openers I find are 16:9 aspect ratio, whereas facebook recommends 4:5 aspect ratio.

  1. Does anyone create 4:5 templates? If not, why?
  2. Am I missing a super-easy way to change a 16:9 template to 4:5?
    Thanks, everyone!