Umm, didnt Skyrim ALWAYS require Steam, even the disc version?
How is anything different?
After Steam decrypted the game game files you could directly launch TESV.exe without opening Steam. Now you can't.
Edit:
Nope, there were ways to run the game without steam if you had the retail physical copy.
Worked for any copy. Even with a retail box version the game files should be encrypted until you connect to Steam.