Insiders bring information to a market. Intelligent analysis and prediction also does, but obviously insiders have special information they are incentivized to bring to the market. Most people placing these bets are simply gambling, insiders and analysts at least have rational reasons for placing bets and add information to the market.
> Insiders bring information to a market [...] special information they are incentivized to bring
Simultaneously: Insiders have power to coerce an outcome, the market creates a corrupt payoff for them to abuse that power.