Excuse me, where are you getting 70 years from? Since the 1920s dating has been a very expected and accepted part of US society. People dated many and for years. My parents were married in 1954 and had several other boyfriends/girlfriends before they found each other and they dated two years before getting engaged. This notion that people regularly got married months after meeting comes from where? Dating was also part of Edwardian and Victorian society, but with more strictures. And again, do some reading, plenty of people dated for ages before World War I. Deciding what history is and knowing it are two entirely different things. If you are talking about women sent to frontier towns as brides, that is an entirely different animal.
And for others, throwing the word "simpler" around is reductive and actually, illogical. Things were just as messy, if not messier, when it came to marriages, property, children and legalities. It's a very smug way of acting like we have a greater understanding of personal relationships in their time than they did and that is absolutely incorrect.