>>14197839
Because a lot of the mods on gunetwork rip models from other games, like the legion one OP posted takes tons of assets from Ryze: Son of Rome.
Without permission from the Devs, like how CD Project Red let people use models from Witcher 2 in Skyrim mods, it can lead to takedowns and possible copyright lawsuits.
So the Nexus, having fairly heavy traffic, is under a fair bit of scrutiny from people keeping an eye on things to prevent assets they made from being used.
>tl;dr
They're not on because copyright reasons.