Unexperienced

Removes XP orbs.

With settings to fit 3 main uses.

Hardcore/Realism Modpacks

Removing xp can be a great way to force players not to use enchantments, either to use some alternative upgrade system, to make the game harder or because it doesn't fit the modpack's theme.

Gating Enchantments/Powerful Items with drinkable Bottles o' Enchanting

Has an optional setting enabled by default to make xp bottles drinkable, providing exp without spawning xp orbs, to make Bottles O' Enchanting the only source of experience, to reward exploration, doing quests or just preventing xp farms.

Lag Reduction

Xp orbs can be very laggy, especially when there's a lot of them an optional setting allows all xp to be given directly to players, avoiding spawning lot of lag creating entities.