Not a huge issue, more of a convenience thing. I stockpile a humongous amount of junk at my main base in sanctuary. From there, I pick up junk and bring it to other settlements in need based on what has to be built. I think it would make this easier if I could automatically turn everything in the workshop into its junk components. If I need 200 steel, 30 circuitry, 25 oil... etc then having everything rendered down into these base components would take away a serious headache.
Again, not a failing of any kind by the design team, just something to make life easier for us obsessive settlement builders.