The same reason that anyone does any risky activity... Adrenaline and dopamine boosts. Riding motorcycles are a calculated risk, one that can make you feel absolutely amazing. You can greatly reduce the risk by riding safely and defensibly. Give yourself space, assume everyone is out to murder you, avoid riding at night, absolutely do not ride inebriated, wear visible gear, etc.
My commute from Oakland to SF was 20-25 minutes in rush hour (1hr in a car), without having to do anything particularly sketchy, just by filtering/lane splitting.
If you're looking at USA stats, you should know that there are many, many people in this country that will regularly get on their Harley, which they've never bothered improving technical handling skill on, after five or six beers, wearing a small plastic hat that resembles a WWI infantry helmet more than a proper ECE/DOT/Snell rated helmet, with jeans and a cutoff leather jacket, and wrap themselves around the nearest telephone pole trying to impress some chick.
If you ride with technical skill, good protective gear, and a respect for the machine and the unpredictability of drivers, you have much better prospects than the stats would suggest.
Oncoming unprotected lefts are the most dangerous feature of city streets, and good motorcyclists learn to be extremely wary of their users.
Re: stopping in front of you - this is one reason why lanesplitting can actually be safer. If a car in front of you does an emergency braking maneuver, you're not pointed at the back of them. Additionally, you're not in the way of the car behind you who was watching Harry Potter on his phone and hasn't yet noticed what's happened. We call the longitudinal gap between cars the "squish zone."
And is one of the primary reasons lane splitting should be legal everywhere, it keeps bikers in the safe no man or car land of the dotted white and lets them not take a full car spot on the red light.
Do you ride motorcycles or is this just conjecture? You seem to be reaching for things to convince yourself of the danger.
You can reduce the danger of rear impacts on the highway, again, by lane splitting at a bit over the prevailing speed of traffic. At stops, you shelter next to, and between, larger vehicles.
When I learned to ride, I was to taught to assume that I was invisible, particularly when at a stop light and an oncoming car was turning left. And proper following distance - for both cars and motorcycles - is to leave enough room to stop if the person in front slams on the brakes.
