I've got 2 stories of when better protective gear would have helped.
One was I was riding my YZ250F at an event called Rumble on the Ridge. I was coming around a corner about 3rd or so and then the bike disappeared beneath me. I went down in a cloud of dust and came down hard on my forearm. It was sore as hell but I dragged the bike off the trail and sat there for a while and watched my arm swell. Since then I've invested in a padded jersey for the bike.
The other was on the wolverine 450 (read underpowered sport utility). I was at a race at the Big Game race property (CRA series) I'm a really slow rider on the ute simply because its a lot of quad to move around and it is on 27' mud tires that get no lateral traction. I was dead last (I'm racing against a bunch of 400's and 450's with a pair of big bore utilities thrown in) as I come up to this hill, I see spectators at the top, the other 2 utes at the bottom and my chance to take my class for the race. I said to myself "pin it to win it" punched it and made it about 10ft up when I realized I was in DEEEEEEEP ****. This hill was steeper than it looked and Im riding a 600lb brick. I make it about half way up before I lose power. I lock all 4 brakes and slowly begin sliding back (not voluntarily). I tap the gas a little to slow the slide. Instead it decides its time for traction, rears up and tosses me. If any of you have read timsyfz's sig, you know what's coming next. I know that I'm about 10ft downhill from my now rolling quad so I ball up and face towards the bottom of the hill. I hear it hit once then it lands on me. I think I caught the rear end of the quad because it was pretty solid. I felt my entire body compress (kinda like how hondaruss described running over his foot) quad keeps on tumbling down the hill, almost takes out a spectator. I was laying on the hill and no more than 10 sec after that quad landed on me, I was surrounded by help. I ended up finishing out the race in like 5th from last. Ended up with a bruised rib all because I didn't want to wear a hard shell chest protector