Why do people get an edge from historical data?

[dropss81]

And outside of Peter's context ...I mean of market context..what horse is fav?
My question is : When I'm looking at a market what things would make me consider a horse is favourite ( It doesn't mean I will trade that horse no matter what) It will help me to decide if to trade that market / that horse.

Thanks

[Anbell]

And outside of Peter's context ...I mean of market context..what horse is fav?
My question is : When I'm looking at a market what things would make me consider a horse is favourite ( It doesn't mean I will trade that horse no matter what) It will help me to decide if to trade that market / that horse.

Thanks

The favourite by definition is the horse with the lowest price.

This can change over time, of course.