Whoever is an inventor and gets to the PTO first gets rewarded. The patent system is an exchange. Inventor teaches the public how to make and use his invention, and the government gives the inventor a limited right to exclude others from practicing the invention. The switch to "first to file" encourages early disclosure, rather than inventing something in secret and waiting to file, or waiting until the inventor's one year bar period was about to run, then filing. Under the new system, if it's valuable and likely that someone else is working on the same system, early filing will be encouraged.