It existed before, but at least in one year, only one or two groups were doing it. Now, everyone is jumping into the trend, and every comeback comes with pre-releases.
Can we just go back to the old days when you got everything on the exact comeback day? Not gonna lie, these pre-releases only kill my expectations most of the time.
If the songs are catchy, and they're certain it'll be a hit, it's fine. But seriously, what's the purpose of dropping B-side material songs?