They are, however, not folk songs because they are utiliarian.

I don't think that in itself is a criterion. Can't get much more utilitarian than shanties and other work songs, for example, songs for getting a job done. Or even lullabies. I can't see how "Miner's Lifeguard" or "Which Side Are You On?" are essentially different.

Copyright considerations paradoxically could in some cases promote the folkification of songs, by ensuring that variants and parodies get transmitted orally rather than through the music industry. Oral transmission is the key to producing variants, because of faulty memory.