I've said it before in a thread on Ike Ike Onay (spelling?):

When the writer writes the lyrics it is not a given that there is one meaning, ambiguity is the lifeblood of creative people. Two or more meaning give the lyric more substance, more worth, more interest. Particularly for the composer, but also for potential audience who cherry-pick their understood meanings.

Throw in aural (or even oral) tradition with the Folk Process and it confuses and sets some of those interpretations.

At the end of the day I guarantee one (or more) of the conflicting meanings above apply equally. The problem is which is which.

Sometimes the composer explains it - eventually! Don Maclean on "American Pie" and he clearly states he was after ambiguity. I think we can all agree, he achieved it.