You are right, I think I now remember reading it from an article that the busienss started in the 1970 and then it was done by those who have more money cause the minimum investment is huge at that time but now affordable because of developments. Forex is a very profitable business.
Yes, actually when it became speculative was around the 70s, late 70s most probably but study has it that it existed even before then but like in a fixed exchange rate measured in the US Dollar and pegged at a gold standard, the rates were not allowed to fluctuate.