It is like this because gold is the most valuable in the game compared to ISO and potions and revives. It is the same reason it is included in money offers and in the summoner sigil. After 6 years you would think the weekly gold (which isnt much at all) would be free.
I posted in the bugs section, but the first round of Halls of Fortune that started yesterday did not require energy. This second round does. I'm curious to know why.