No legal tackling, there are all kinds of trips, accidental headbutts, kicks, etc.
One of the worst things I've seen in soccer is a shin bone break in half from two people kicking at the ball. Soccer players, football players, almost any other athletes dont condition themselves to withstand impacts the way MMA fighters do. Take tito's killer core workouts, thats designed to prevent injury just as much as it helps his stamina, same with strengthening your shins, etc.
Basically, MMA has the most safe rules, the most well conditioned athletes(in terms of preventing injury, soccer is very demanding), and is in the best situation to get help if it is ever needed.