wearing full armor seriously reduces - but does not prevent - injuries from inevitable crashes. I was thrown off my Ducati at 70mph in July, hit the road hard and tumbled. I rode home, then went to the ER the next morning. Three broken and displaced ribs, and water on the knee from bruising (my knee hit first). Not a scratch or bruise anywhere else on my body, and the ER doctors could not believe that I got away with just broken bones from a crash at that speed; the trauma physician told me at those speeds patients generally suffer permanent injuries.
the ribs were a pain to heal from (not the first time I've broken ribs) so it wasn't a mild accident. for two months I was cursing the hard suspension ride I had set up in my RS6, as the bumps would jar my healing ribs with some pretty sharp pains! but I know a guy who lost control of his bike on the highway last month wearing a riding jacket and helmet only, and his sneakers flew off and the chain ate his foot up real good. they screwed it together with a pretty impressive amount of hardware, but it's not taking, and he's scheduled for a below-the-knee amputation in three weeks.
my dad, as a physician, isn't particularly a fan either of me riding; one of his partners in his practice wrecked with his wife when they were in medical school, and while he recovered, she was paralyzed from the waist down. Because of that incident, he chose his specialty - physical medicine and rehabilitation.
but the riding gear, if you're willing to invest a few thousand dollars into it, is pretty impressive these days. my boots are designed to prevent torsional forces on the ankle. my knee armor took a blow that should have shattered my knee. my gloves are half carbon fiber and have wrist supports to reduce the severity of a wrist injury. hell, there's even a support to reduce the chance of breaking your pinkie finger and padded stingray leather on the palms. my spine is protected down to the coccyx, and there are even clavicle protectors. kevlar and kangaroo leather has kept me from ever scraping my skin. airbag suits are used by racers but are still a couple years away from street use (due to the sensors required for deployment).
what's not covered: I don't always ride with a sternum plate, and I don't use a cervical brace to prevent hyperflexion of the neck (neck injuries in street riding are extremely rare, but common in extreme off-road motocross riding).
my bikes are also equipped with some very bright lighting. Harley riders will claim that "loud pipes save lives", but what really helps drivers see you is lighting, not sound.
it's also notable just what kind of equipment comes on bikes these days. my Ducati is pretty old, so it's not forgiving of any rider errors. my BMW however, is both the most powerful superbike on the market, and carries the most comprehensive electronic safety package. ABS is standard on BMWs, and my bike has a pretty sophisticated traction control system that can strongly reduce the chance of losing control on slick pavement. Three gyroscopes measure lean angle and if the front or rear wheel is lifting, and the engine cuts power accordingly. For years only BMW offered such safety equipment on their bikes, but other makes are beginning to offer these systems as well.
it takes a good 10 minutes to gear up before riding, and it's very hot during the summer to wear all this armor. but it definitely reduces the risk of dying (not crashing) from the body shutting down from multiple injury trauma.
and I am an organ donor btw. it's not the safest mode of transport, but with the right gear and some common sense, the odds of dying are about 20% higher than driving a car. not everyone is comfortable with such odds, but I am.