Before entering the debate on marriage, I think it is fitting to discuss where it starts– the engagement ring. An engagement ring is the current custom to start the official track to marriage. This practice is very modern. Before the 1930s, this was not a common practice. Statistics on diamond sales are not very good until recent years, but it looks as though the use of engagement rings increased sharply during the 1930s and 1940s and peaked in the 1950s, and have declined since (see David Friedman Hidden Order).
American diamond companies did not ramp up advertisements and it was not America’s new sources of wealth after WWII that brought about the increase in sales. Margaret Brinig, an economist, proposes an amusing answer (see journal article here). The legal climate was changing because “prior to 1935, 47 out of the 48 states permitted action for breach of promise to marry”(Freidman, 321). Despite what you may think, sex between engaged couples was common– yes, even prior the 1930s. If a woman was to lose her virginity during an engagement and the husband-to-be changes his mind, a woman had the right to sue for damages– after all; it greatly decreased a woman’s opportunities for marriage and with limited economic opportunities for women– it can really spell trouble. However, between 1935 and 1945, the action of breach of promise was abolished in states containing about half the United States population. This is where Margaret Brinig comes in. She argues that this is the reason for the increased sales in engagement rings. If a man broke her hymen and their engagement, the woman would keep the diamond ring ( which acted as a substitute when “breach of promise laws” were abolished) as compensation.
I guess it started off less about love and more about economics.