I think routes are fundamental to most VNs, it's what make them special, "If I choose this, what happens?". In anime and manga that has several target characters they often just publish the "most important one" or true route. But different viewers/readers like different characters and would choose differently. That's where VNs with routes stand out.
And as a bonus you can get unlockable routes where it's done right, where the VN is like a ball of yarn, or a matryoshka. You learn more and more, until you finally understand it all.