It hasn't been officially said why the move was banned by WWE.
On the April 20 edition of Monday Night Raw, Nia Jax performed the maneuver on Kairi Sane. The spot drew criticism for the manner in which Sane awkwardly hit the middle turnbuckles.
The most infamous moment involving the move came at the 2015 Night of Champions pay-per-view, in which then-WWE champion Seth Rollins did the buckle bomb to Sting. The move resulted in a legitimate neck injury for the 56-year-old, for whom it ended up being his final match. Sting was ultimately diagnosed with cervical spinal stenosis, and admitted on a podcast with Ric Flair that he was lucky that the injury wasn't "catastrophic".
Several AEW talents have used the Buckle Bomb in their arsenal, including Kenny Omega and Brian Cage.
WWE has reinstated several previously-banned moves in the past, namely Rollins' Curb Stomp. It has also allowed, on rare occasions, for banned moves to be used, such as the piledriver.