My response to "Why do Nikons use H 0.3, 0.7, 1.0 and 2.0 instead of ISO 12,500, 16,000 etc." were always answered with, "Because the ISO (International Standards Organization) does not recognize any film or digital speed higher that 10,000. So to avoid getting into trouble, Nikon uses the H designations."
Well, my theory worked until I got my D600. And instead of finding ISOs of 50, 64 and 80 (familiar ASA numbers from my film days), I find L 0.3, 0.6 and 1.0.
Obviously, ISO speeds of 50, 64 and 80 exist and are perfectly acceptable by the ISO. So why use the L system instead of actual ISO ratings that have existed for years?
I hate when people ask me what I see myself doing in 5 years...... I don't have 2020 vision!