[Rav Eliyahu Lifshitz][1] of [Maaleh Adumim][2] [explains][3] that this is based on a fundamental conceptual difference between "*shehakol*" and the other *birchoth hanehenin*. He suggests that really only plant life (*tzome'ach*) was originally created for consumption. Thus the *brachot* - "*borei minei mezonoth*"/"*borei pri...*" suggest thanking for the creation of foodstuff. "*Shehakol*" is more an acknowledgement that even these things that were not primarily created as our food, also are created with His word and deserving of this recognition.


  [1]: http://www.ybm.org.il/default.htm#/article?Item=757
  [2]: https://en.wikipedia.org/wiki/Yeshivat_Birkat_Moshe
  [3]: http://www.toralishma.org/wp-content/uploads/2014/01/%D7%91%D7%A8%D7%9B%D7%95%D7%AA-%D7%94%D7%A0%D7%94%D7%A0%D7%99%D7%9F-%D7%9B%D7%98.pdf