Why are there medals excluded from arena?

I was wondering why there are some medals in warzone that are excluded from arena. For example the assist medal I really enjoyed knowing that I got an assist rather than looking at the kill feed for that small arrow. Also I really enjoyed killjoys (which are not included in Warzone… But assists are) I also used to really enjoy shotgun spree sniper spree etc… I do remember the beta though and the medals were non-stop I am just wondering though if they are going to implement these medals back into arena or just keep them for war zone only… - thanks.

Because the community requested them to be.

Back in beta it was medal spam galore.