Energy-based Champions

So I just bought Zed, and I really love his play style. He can deal lots of damage, and, being manaless, he can stay in lane so much longer than other champions. There is one huge shortcoming though. I assume this is the same with other energy-based champions (except Lee Sin, because of his passive), but the lack of energy scaling is sad. You start with 200 energy, and you end with 200 energy. You start with 10 energy regen/second, and you end with the same. There are no items that can buff this, meanwhile every mana based champion can stack mana and regen and spam their abilities to their hearts content, while I'm just sitting here with Zed, having spamable abilities that use a fourth of my max energy. That doesn't make sense to me. I know there are runes and whatnot, but I don't want to buy and entire rune page for one champion. Can someone help me understand the reasoning behind this mechanic?