Think about it this way, actors in financial markets all have various beliefs about the future, and all of these beliefs are on a scale of accurate to inaccurate. Speculation allows these beliefs to be aggregated into a single market price (which btw implies no arbitrage) for various types of contingencies and risks, and the price will rapidly update to reflect updates to reality and thus updates to everyone’s beliefs.
Think about it this way, actors in financial markets all have various beliefs about the future, and all of these beliefs are on a scale of accurate to inaccurate. Speculation allows these beliefs to be aggregated into a single market price (which btw implies no arbitrage) for various types of contingencies and risks, and the price will rapidly update to reflect updates to reality and thus updates to everyone’s beliefs.