Why do scanlation groups dislike mangago?

I've seen multiple rules like: "do not upload on ***" why is that?

Are the groups having negative experies with those sites? I think that shouldn't be the case since they'd be less popular without them

Are there any law breaking endangerments? Since they are publishing on a different site it's still illegal (just like reading)

Reasons i listed above may or may not be true so it'd be nice if someone confirmed or denied them

I have no intention to offend anyone i am genuinely curious
And im sorry for any mistakes im not native