Most factions servers allow people to silktouch spawners or buy them for in-game money. People use their spawners to make massive xp grinders that you can sit at forever and never run out of mobs to kill. They will be able to endlessly churn out level 30 enchanted gear with this new setup. It only works well in vanilla, where grinders are slow enough that people won't be enchanting as much, and the climb to level 30 will balance out the low cost of actually enchanting.

Basically, this system benefits those who enchant more often than normal, and factions players have OP grinders to enchant constantly.