Those on the academic side of agriculture may have a different perception of foliar fertilizer applications. Very little work has been done in the U.S. universities in regards to foliar application, and not only because it is applied research, which is not favored by U.S. universities. Based on a limited understanding of plant physiology and the emphasis on soluble fertilizers combined with a hydroponic mindset, they just didn't want to believe that that tiny amount of fertilizer would have any effect on crop yields. We now know how it works - it works on the cellular level to stimulate chlorophyll production in the cells contained on the leaves most exposed to direct ultraviolet irradiation. The increase in the pigments in the cell including chlorophyll could more efficiently convert sunlight to energy which in turn stimulates uptake from the roots to the leaves.
Additional production afforded by dark pigmentation protects the plant significantly.
The use of foliar fertilizing in agriculture has been a popular practice with farmers since the 1950's. They knew it worked but were told it shouldn't work because so little fertilizer was being applied per acre. It has only been recently that research has been done that shows how a small amount of potash or phosphate applied by foliar spraying can increase the yield of crops so significantly, actually providing a better return per dollar invested than soil applied fertilizer. Foliar fertilization doesn't totally replace soil applied fertilizer but it does increase the uptake and hence the efficiency of the soil applied material. The increased efficiency can reduce the need for soil applied fertilizer and reduce leaching and run off of fertilizer nutrients, reducing the impact on the environment of fertilizer salts.