I ran Simulations Publications, Inc (SPI), a company that published over 400 of these games while I was there (1969-80). Most of these were wargames. Peace games don’t sell as well, which says something about us all. We’d rather fight. Kill for peace and all that.
Manual games kept the designers honest, as the players could see how the game worked and figure out for themselves if they thought the designers approach was on target or not. Computer wargames plunged the games’ inner workings into darkness.