So are we saying that "It's a long way to Tipperary.." and the like are on their way to becoming folk songs because people have enjoyed and do enjoy singing them? Is "usage" the ONLY criteria

If so, then I fear in the next century, we (I use the term hopefully) will be singing folk-songs that sound remarkably like "I just called to say I love you" and "American Pie"...

Heaven forbid!