why some manga pages have their scanlations removed?

[forever_may]

this is what i'm talking about:

this is the manga page for watari-kun no xx ga houkai sunzen. as you can see, there are lots of missing scanlations here but this manga page used to have complete english fan scanlations as well as fan scanlations in other languages.

and it's not just this manga either. i noticed there are mangas that have their fan scanlations removed like 2.5 Jigen no Ririsa for example. why? what happened?

 

[Ferreas]

Mangadex gets hit by DMCA - more than 25% of chapters gone | staff FAQ update
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