People currently spend about 9% of disposable income on food as compared to 24% in the 60's -- so what you suggest is happening to some degree: http://3.bp.blogspot.com/-Uz4mKJv2dWQ/T_B-DGnY34I/AAAAAAAATt...
This is because, and I know this statement is controversial, America is radically wealthier at all levels in 2014 compared to 1974.