Workshop has taken off a bit here and there, but it's worth remembering that basically when Steam Workshop was primed to take off was when Skyrim modding was becoming mainstream. I don't know the specifics of it, but I think the Steam Workshop had some "paid mods" and that rubbed everyone the wrong way during a time when modding was not monetized.
There is a bigger question that is unsolved, both ethically and legally. If someone makes a Skyrim mod: (a) should the creator of the mod be allowed compensation and (b) should the game developer be entitled to garnish some amount?
I have my own opinions, but I think the community doesn't really trust that a mod put on Steam will be available tomorrow for the price and under the conditions the mod creator envisioned.
Paid mods are problematic because what happens if a game update breaks the API the mod uses? This frequently occurs in many games. Suddenly you've got an unhappy customer, and with money comes liability.
I doubt any game developer would want the burden of being liable to maintain backward compatibility for old mod APIs to support third party mods, but if they take a cut of any money then they ought to be responsible for maintaining that.
Part of the reason KSP has ironically had a modding renaissance is because the community knows that there won't be any updates which could break some of the more ambitious mods being made.
There is a bigger question that is unsolved, both ethically and legally. If someone makes a Skyrim mod: (a) should the creator of the mod be allowed compensation and (b) should the game developer be entitled to garnish some amount?
I have my own opinions, but I think the community doesn't really trust that a mod put on Steam will be available tomorrow for the price and under the conditions the mod creator envisioned.