Well first of all muscle is your armor. The stronger your muscles are the more protected your joints will be.
Power is the foundation on which speed and agility are built upon. And strength is the foundation on which power is built.
Athletes who are naturally super explosive might not need a lot of strength work to be fast and agile. Which is why you will see a lot of star players not do any strength work... in all honesty they don't need it to be fast and agile because they are naturally at the top of the food chain in these department.
That's the problem. Onlookers will look at what the stars do and generalize that it's optimal for everybody.
Since you don't need maximal strength to play soccer if a player is naturally explosive, fast and agile it is true that he might not need strength training. But any athlete who doesn't have that natural explosiveness will need to strength train to become more explosive.
To be clear the less naturally explosive you are, the more relative strength (strength level for your body weight) reserve you will need to become powerful.
So an average athlete who decides not to strength train because some top players do not, will likely severely limit his development.