It's also because these companies hire away staff all the time. Rule 1 of working in this field, recruit a mid level member of the other company's research gro

It's also because these companies hire away staff all the time. Rule 1 of working in this field, recruit a mid level member of the other company's research group biannually to get the latest gossip. It's impossible to keep a 1 page or shorter "algorithm" secret, when the creators are geniuses and they hop jobs every year or so. Fellas with more IQ than games in a baseball season, they just don't forget.