Imagine yourself throwing on a smooth wet surface. Now, would you want to be landing on your heel then?
It "might" appear that some land on their heel first, but they transfer all their weight onto the rest of their foot. Being able to transfer the weight onto the ball of your feet will give more stability to the front leg.
Landing on your heel usually means something's wrong in your delivery. It can also lead to opening up the hips and shoulders too early.