Following chanteyranger's focus on use, I'm surprised I haven't heard the one word that sums it all up - TOOL.

Shanties were tools used by seaman. Different tools USED for different jobs. Not all jobs needed these kinds of tools. Technology eliminates the job and the tool falls out of use. Good tools make work easier.

People, including seaman, didn't tend to bring their tools with them when they're out on the town. Songs and and singing were for church and music halls and family parlors - places where tools weren't generally carried. When you think of it as a tool you can understand why an old salt, knew hundreds of shanties might say he didn't know any songs.

You might also frame lyrics and any musicallity as just decorating the tool box - sort or auditory marlin spikesmanship.

Any thoughts?