In a lot of traditions, initiation comes with death & rebirth. This could be psychological, spiritual, or physical.
Some experiences can be so overwhelming, so paradigm-shattering that everything in the past feels like a distant dream and you've suddenly come crashing into a new, fantastic and brutal reality.
Formal initiation is just ritual, it's meant to induce an inner revelation and rebirth, done without spirit it's as meaningful as communion at church, just rote bullshit, a milestone box marked off on a checklist.
People report going through several initiations, with each deeper Gnostic revelation. In the Merlin tradition, initiation comes with looking directly into the "Eyes of the Dragon".
The "you" that gets the benefits and edges gets nothing, because that you is dead. Someone more alive, true, and powerful gets born.
Sometimes a non-physical entity may initiate you as well, not just a temple or Master.