It's true they are "just" summarizing current knowledge. But there are better and worse summaries of current knowledge!

Some summaries, like on some prediction markets, have objective accuracy that is much better than chance.

Sort of. Putting current knowledge into a number can be pretty interesting / useful though. Like many people, I read headlines and pay attention to what's happening in international politics, but from those it's hard to have any sense of how much reality there is to bluster in Iran/Panama/Venezuela/Greenland just from general discourse and media. For me, prediction markets have been very helpful in offering some sort of grounding beyond the general noise in areas where I have very little intuition or realistic sense of the possibilities.

I tend to go back to this article when I discuss these markets with people https://en.wikipedia.org/wiki/Wisdom_of_the_crowd ... in particular, these markets are designed to tease out the "surprisingly popular" answer https://en.wikipedia.org/wiki/Surprisingly_popular because they incentivize divergence from average response.

I don't understand the distinction you are making.

Obviously they are based on current knowledge. Nobody has any actual crystal ball.

But the outcomes are with regard to future events. So the correct term is predictions.

And they don't "just summarize the current knowledge". The whole point is that they better reflect the knowledge of people who presumably know better because they are willing to put their money where their mouth is, and ignore the vast majority of nonsense. That's not summarization. That's judgment. That's the whole point.

>as the data shows they largely just summarize the current knowledge, with little predictive ability.

What counts as "little predictive ability"? Do weather forecasts count as "predictions", or are they "indicators" too? Sure, they might have a more consistent track record, but then again weather is less susceptible to human interference than whatever happens in geopolitics within the next year. Prognostications about future climate might be less reliable, do those have to be downgraded to "indicators" too? On the flip side, prediction markets have a very good track record when forecasting certain events, such as interest rate decisions. Does that mean whether it's a "prediction" or a "indicator" depends on what you're forecasting?