>>713131461
It was a counterpart to Fusion back in the Ye Olde Fusion Deck days. Fusions required specific monsters to make, Rituals could use anything with enough levels as tribute but you had to have the Ritual monster. Of course that just meant they were both shit because you spend way more resources on a monster that loses to Sakuretsu Armor like everything else.
Fusions eventually loosened up on material requirements, and the ED turning into a toolbox/where the actual boss monsters are stored meant decks were designed to always access them. While Rituals were stuck with Manju/Senju pretty much intentionally being their best normal summon before Diviner and the innate hand disadvantage to overcome meant the monster had to be extremely powerful one way or another to be worth summoning. Or cheat (and even then, the Drytron Ritual monsters aren't that good).
And no, you still can't put Rituals in the ED because then we lose Prep and Pre-Prep and Manju/Senju and a dozen other support cards that they benefit from due to being in the main deck and you have to errata like a hundred cards and now all those decks are nerfed by ED max size anyway. Rush Duel only got away with it because they got to write the rules from the ground up.