What's the history of male intimacy like? I know post WWII American context like McCarthyism and the Stonewall riots. But I've never poked my nose before WWII. How about the roaring 20's? Your collection always reminds me Jason Lutes' "Berlin." It's a graphic novel set in Berlin on the verge of Nazi Germany. He depicts male and female intimacy as a part of Berlin everyday life along with workers, fascists, bourgeois, food, drug, Jazz, etc.
Funny you should ask -- I'll have to blog about it. The short answer is that as gay and lesbian people have formed a movement and become more visible, intimacy between men has become judged as "gay" and thus pushed out of the mainstream. The vast majority of the images pre-WWII of men together are friends who are unburdened by modern homonegativity. The same has gone for countries in the Arab world. It wasn't so rare even 10 years ago to see men walking down the street holding hands. As the western world has become more available, and men have feared being labeled gay (horrors!), they've stopped holding hands. It's sad, really, how constricted friendship between men has become.