Mr Gravity is just waiting for those that don't.
So is Mr. Murphy. I'm 26 and never use to wear anything. I had taken a small 10 footer from a ladder stand when I was about 20. not a big deal but the ground was soft and I ddin't land on anything. Now I'm married and have a two year old son and another little boy due anyday I feel a touch more responcibility. I'd like to be able to pass along the hunting tradition a opposed to eating out of a tube.
Play it safe. You may never need a harness but it won't kill you to wear one.