THE MARKET SHIFT
"WHY" has the question of quantity vs quality come about...
Relationship marketing has been around a long time. The local grocer, barber etc in the 19th/early 20th centuries.
Advertising:
Then advertising became more popular due to the speed of results.
Relationship marketing was considered time consuming and expensive in contrast to advertising. (Staff costs, time to ROI ETC). Relationship marketing is a long-haul strategy.
Now, with advent of social media, tech and automation. The decrease in cost, increase in tools, platforms available means it's highly accessible once again. I.e it can often be easier and more cost effective to implement than traditional ad based strategies.