I agree, for me it does not pose much of a challenge to install a mod. However, not everybody has the knowledge to mod their games. Who is anyone to say that these people do not deserve the chance to play these amazing mods just because they don't have the skill set to apply them? A lot of people do not have Skyrim on Steam as well, so that is irrelevant. Also, correct me if I'm wrong but Steam workshop is a Steam feature not Bethesda... and mods don't really "benefit" Bethesda in the first place per se... (correct me if I'm wrong) Bethesda would ultimately benefit if such a system was installed too. I could foresee an increase in sales of Oblivion on steam just because of workshop integration; a revival to an older game claiming more players that came from Skyrim.

I just would like to see an increase the ease of installation and exposure of the Oblivion modding community, which I don't think anyone should not want. I respect the fact that this is a far-fetched wish, but I don't think there would be any harm in trying for it.