As they’ve said in the past, there simply wasn’t time for “previously on the life of Steve Rogers.”
Elsewhere in the interview, the screenwriters said that anything that didn’t really propel the plot forward of the fast-paced film had to go.
But despite the function it would have served, addressing a lingering plot thread and providing some background for what Cap was up to and where he has been in the two years since Civil War, this part of the script got the axe.