The earlier you know the better. For example some people want us to make changes to forestall global warming now, not when the droughts and other predicted effects have "definitely happened".
That's just science though. Like, we can speculate with a high degree of certainty that in billions of years the Sun will turn into a red giant, likely ending any life that exists in the Solar system and then cool down, in spite of how far in the future that is. Non-living things behave in very predictable ways once you understand the laws of physics that govern them. Humans and their activities are very complex and much harder to predict.
With markets, there is no need for the inference to be explainable to any one person, much less a layman. We just let a bunch of overconfident monkeys make their assertions, and after some time we cull the ones who got it wrong. The ones who are correct get more votes over time. Why were they correct, are they using insider info? Who cares.
So the argument is that the system will financially reward people with the ability to make correct predictions, but we all benefit because we can use them as oracles to predict the future (to some extent at least) and adjust the prices accordingly (and prepare in other ways). I don't know, it just seems impossible to make any sense from all the chaos. It seems especially hard to make any sort of accurate predictions of what the current administration will do next. I can believe that there are political-economic experts out there who can make some accurate predictions on the implications of the Maduro capture, but these people are academics. What I'm seeing from business people now is mindless short-term thinking, endless hyping and trend-chasing. In the financial crisis there were people who recognised ahead of time that there was a property bubble and made a lot of money from this. Has their savvy and foresight made us all collectively wiser? What I'm seeing now is a bunch of people mindlessly pouring a ton of money into the AI bubble, so doesn't seem to be the case to me.
This just seems like a gambling addict who convinces himself that he has savvy and a nose for things, before losing all the savings and having collections agencies call every night.
But let's suppose that you're right and there is some darwinian system that allows people with wisdom and nous and connections or whatever to get the info they need to make correct predictions, rewards them financially and lets us all benefit from their ability to make predictions by listening to them more next time, or at least by having smarter people having control of the most money. Let's assume for now that they've predicted things correctly because they were smarter, that their smartness, if it exists, benefits society, aside from any other of their qualities, let's set all these question aside. In that case, how does insider trading fit into this system? People who got inside information did so because they lucked into being in the right place at the right time, not because of ability to make correct predictions. They won't be able to make correct predictions next time, so the darwinian system ends up rewarding people with lower fitness.
There are also other considerations. Let's say that there is a secret operation being planned against a foreign leader and let's say that this operation is something you want to succeed. Let's also say that the foreign secret service is smart and checks the prediction markets and is able to detect a pattern that points to significant insider trading betting on such an operation taking place in the near future. Wouldn't that tip them off ahead of time that this operation will take place, possibly resulting in this operation failing completely?