With the advent of mass production, mass advertising was invented too. In the 60s, the goal of most marketing strategies was just to get as much views of their ads as possible. Television spots and street posters were the most popular media because with those means of communication marketers could easily and quickly spread their message throughout the whole country.
These were the days of glory for marketing agencies like the fictional Sterling Cooper Draper Pryce in Madmen; these agencies could make big money with a poster and a catchy line directed to the general “frustrated housewives” category of consumers. The segmentation was mainly demografic: marketers based themselves on age, sex, income and such other general features...
No need for me to tell you that their business model would never work today. It has become increasingly complex to segment a market in any sector. Also, the overload of marketing messages that consumers have been bombarded with over the last decades has made them much more insensible to any communication, so to reach them you really have to stand out.
This is why it’s important to really know who you are targeting, so that you can give them something thats truly interesting.