Years ago it never occurred to me there were different bobbins for different machines, or that it mattered how they went into the machine - I just popped it in and sometimes the machine worked well and other times it was a royal pain. Once in a while I would have a bobbin that would not fit onto the bobbin winder and just thought I bought a cheap knock off. So needless to say, I have a small collection of my own, because it's not in my nature to throw anything away.
My ignorance truly caused for some very frustrating sewing days.