Parachutes make good sense for formation flying, air racing (except F1), glider flying, indeed in any situation where aeroplanes will be in close company, the risk of collision is high and the relative speed should one occur will be small.
Most of the time when I'm in formation, it's below 100' and a parachute would do no good...just like it would do little good for an air racer. That said, occasions have passed in which a damaged airplane was able to be climbed high enough to jump, saving the pilot and putting the aircrat away from a populated area, when air racing.
So far as a helmet...regulations require that I wear one, and last year I was glad to have one on during a turbine engine failure that resulted in a forced landing on a hillside. The failure occured at 150' AGL, an offered little opportunity for the use of a parachute.
Aerobatics are another matter entirely, and it is there that a parachute certainly should be worn.