[mrr54]

In practice mods are definitely released outside of Steam Workshop. I don't think I've ever used Steam Workshop for a Skyrim mod for example.

[BlueTemplar]

Skyrim had mods before Workshop even existed. Things are very different for games released with Workshop support.

[mrr54]

In my experience they aren't different at all. Steam Workshop is just a distribution platform for mods. It's a mod installer and manager. It doesn't stop you doing it manually.