>>42992449Because Lugia/Ho-oh used to dwell in Ecruteak. It's implied Lugia accidentally caused the storm that burned down the towers and the two fled. Lugia and Ho-oh are their local gods, and getting them to show up is a sacred ritual.
It's done better with Ho-oh than Lugia, but GSC was doing this before it became a requirement. Legendaries aren't well understood and hide away from human eyes, and are often venerated. It makes sense that to encounter them you have to undergo a mystical rite, or for it to be a chance and difficult encounter. Before they started throwing legendaries and mythicals like crazy anyway.
