Because in most cases they can only do the thing they do, because another company invested millions in order to make, release, promote and support the game. Without their work, the modders would have nothing to mod. Because working out a licensing deal with every modder to split the revenue is a lot of work and most mods won’t get played much anyways, it isn’t worth the hassle. So in order to accommodate the community and keep their game active for longer, the terms are modding is allowed and even encouraged. But the other side of the bargain is that the mods can’t be sold. And usually the company reserves the right to outright ban mods using legal means. For example when people mod in far right extremism the company doesn’t want to get associated with.

Now there is a gray area where people donate to modders or even pay outright for modders to build certain things. This is usually just fine, as long as the mod is also available for free. People aren’t paying for the mod, they are paying for the dev time, which is totally fine.

But this modder specifically put access to his mods behind his Patreon. Sure technically you could subscribe for a month, get the mod and then stop the subscription. But that’s legally still a pay wall and in practice the mod needs to be updated often to keep working.

So it’s pretty simple in this case, the modder was asked to stop putting the mods behind a pay wall, he didn’t, so he got a cease and desist. Usually I’m all for the little man and against the large companies, but in this case the terms were pretty clear and the modder violated them.

Now we could have a more general discussion about how and if modders should be compensated for their time. But I feel that’s a bit beyond this single case.