Source: https://twitter.com/monsterhunter/status/1729672458775519663
Edit: From @ISolox@lemmy.world 's comments below, it seems these are free DLCs which you can download as soon as you start the game. So, they aren’t removing any paid content, only free DLC.
The base game (to access these quests) is $40 for a brand new copy. It’s only $20 if you get a used copy.
These DLCs event quests are also free to download.
Still sucks they are being removed, but these were minor free 3rd party event quests to begin with.