After my Mum died in 2007 my Dad suddenly opened up about his war years.
Had exactly the same experience with my Dad, he was in the Seaforth Highlanders and only talked about his experiences really just a few months before he died.
Except one Sunday afternoon in the 70's we were watching a programme called 'All our Yesterdays' when he suddenly shouted thats me! he had been filmed supposedly in Belgium somewhere in the early years of the war but in actual fact the footage was staged in France after the war had finished. Wish I could find the clip, he was dressed in a Kilt holding a revolver looking around a corner.
I think those that saw terrible things just did not want to talk about it, there was of course no support in any way for men like him after the war.