I would guess that the vast majority of the population do not take meaningful actions based on election prediction (other than "I might [not] need to actually vote").

There are good reasons to have polls and predictions but they are far from necessary.

Just because something isn't useful to everyone, doesn't mean it isn't useful to someone.

The original claim was that election prediction is useless -- are you willing to concede that election prediction isn't useless?

I made no such claim. I merely stated that this particular election prediction was useless.

People who work for political campaigns need to know, businesses and investors might like to plan, etc.

Yes, but it is not "needed" in the current form. It is needed the same way you need to predict how global trends will be in 6 months: very important for a lot of people, but not an actionable information for most.