The idea is to spend the fewest resources outside of what you already have in your collection to construct a deck
The only other one mana card quality spell that is instant is the highly contested Brainstorm, Opt is meek by comparison but nevertheless effective
The sideboard fetch is tempting enough, but, again, thats asking a lot for 5, as is spending the resources to defeat a battle with 7 defense
Not only do you want to cast it because of all the cascade triggers, but you also want to cascade into high mana value spells
(This is why I love FromSoftwares games so much: from Dark Souls to Elden Ring they never get easy or predictable.) Here is a small selection of games from the past year that I abandoned in this way, not long before the end: Indiana Jones and the Great Circle
Neither half of it is particularly amazing, but having the ability to choose either is great