You are right about the doubleheaders. Browsing the standings I first thought there must have been an awful lot of rainouts in 1938. Then I realized they were scheduled that way. Most weekends most teams a doubleheader. Today the doubleheader has gone the way of the complete game pitched.
Like everything else it’s a money deal. 2 games for 1 ticket price loses money. So yes, it’s gone the way of the complete game. And, as long as major league games take today, who could stay at the park for two games? I love the game, but that’s a bit long even for me.