People will have the option of knowing that a vote for their preferred party is not a wasted vote.

Then if their preferred party is eliminated early, they still get to say who they prefer from the remaining parties.

This point is worth a few seconds of thought. You may well ask why vote for Green (for example) as your first choice, knowing full well that in your area it will be eliminated and your second choice is the only one which stands a change of being counted. Is it just a sop to your conscience that has no real effect?

I would say there is more to it than that. It gives information that could be used by winning candidate to influence their actions in that term and when they decide who to court for the next election. It also allows the Greens (in my example) to see if support is growing or falling and act accordingly.