since black holes are incredibly common in the universe, if everything that went into a black hole came out the “other end” from a white hole, then it would logically follow that white holes would also be incredibly common. however, while white holes might exist, nobody has ever observed one, or found any mechanism capable of creating one, or evidence suggesting that they even exist, or have ever existed, or will ever exist. meanwhile, we have directly imaged the accretion disk around a supermassive black hole.

one definitely exists, the other is firmly within the realm of theoretical only, where it is expected to stay indefinitely.