Why, until recently, were smooth nose sections not popular?
Because it's bloody difficult to make the curved shapes out of the materials used until recently, with the technology available at the time.

The few aircraft that had it in the past generally were very expensive and labour intensive to build, compared to competitors, and therefore not economically successful.
Now, with improved manufacturing techniques and materials, plus the rising cost of fuel, it's becoming ever more viable and more such are appearing.