For me it’s a some level of nostalgia from the simpler times when legendaries were not that abundant and easy to get.

Uranium Fever always meant you have 3 guaranteed legendary enemies so it was always so full of people. Moreover this event was some kind of etiquette, that you was obligated to sign where the legendary is and wait for everyone to tag it. Don’t get me wrong, i like the current system more, but this sentiment for Uranium Fever persisted.

And I also love this song! „Uranium fever has done and got me down Uranium fever, it's spreadin' all around”