Sniping is looked down upon for a number of reasons. One of the ones most significant to the readers is the fact that it often results in series being abandoned entirely. A new group comes in and starts pushing out faster translations than the established people, the established people quit because why should they bother when someone else is doing it faster and people clearly aren't appreciating the effort they were putting in, then the new person who picked it up on a whim quits because they don't have the attention span to keep it up long term, and suddenly there's no one translating the series.
The old translators will likely have picked up some other series in the meantime, so they can't come back to the sniped one, and so the readers are left begging for someone, anyone, to come in and resurrect their beloved series. It is quite common that no one does, and they're just left with nothing.