Some companies allow the use of their content, normally as long as it's not charged for. Other companies refuse outright and may take action if they find out someone has used their work without permission (removal requests/DMCA orders, etc).
Some are 50/50 - they'll allow the use of "some" stuff, but not others, this is usually due to contract restrictions, or them having used third party material themselves (with permission). Good example of thatis games that use licensed music - they have permission, or have paid to use band's music.
That doesn't permit someone that owns a copy of that game, to take the music from it and use it in another game as a distributed mod just because they want to. You need permission from either the game devs, the music artist/band (or their producers) - on in some cases, both.
Take GTA and it's radio stations as the example - Rockstar paid to use all that music for their ingame radio stations. You taking that music, putting it in say, Fallout 4 or Cyberpunk 2077 and sharing it online without their written consent is when it becomes a copyright violation and content piracy.
If you ask a company if you can use their content and they don't respond, or do but say "no" - then that's it, you legally can't use it. You need a clear and confirmed "yes" on the matter.
Also helps if you can prove you have permission.
-and as others have said, just because other people have done it and they've not been removed yet doesn't mean we allow it. We can't check every upload as they happen, so we do indeed rely on people reporting mods they believe are breaking the site rules. So "but others are doing it" is not an accepted excuse or reason complain when a file is removed.
Site users are expected to have read and understand our site rules and policies, they are very clear on the matter of using copyright material.
https://help.nexusmods.com/article/28-file-submission-guidelines