Why do people always make Bill O'Neill's Sandwich into a metaphor for life?

Bill O'Neill's Sandwich
made with so much love and care,
he was so concerned to make it,
a fest of such unrivalled cheese and tomato culinary flair

Bill O'Neill's Sandwich
with tomato sliced so precise
and he took the time and trouble
to grate the cheese so carefully, after all, it was Caerfilly

Bill O'Neill's Sandwich
and he topped it off with herb
then he went and cut the crusts off,
cos the girl he fancied liked it like that or so he'd heard.

Bill O'Neill's Sandwich
Bill O'Neill's Sandwich
Bill O'Neill's Sandwich

Bill O'Neill's Sandwich
met a tragic, sordid end,
A triangular projectile
that intended to offend,
He put a bit of spin on it,
ensuring it would bend,
This half-eaten snack was thrown by Bill, he was no friend.

Bill O'Neill's Sandwich
It thought it was a hit,
as it shared the limelight
with Smeggy and the Cheesybits, but they ignored it.

Alienation.
Fulfilment has not worked for you.
Rejection by your maker too.
Ignored by the people you were meant to smear.
Left on the floor decaying in a pool of beer.
Humiliation.

Bill O'Neill's Poor Sad Sandwich
Bill O'Neill's Poor Sad Sandwich
Bill O'Neill's Poor Sad Sandwich
Bill O'Neill's Poor Sad Sandwich