Definition of accident:
ac·ci·dent [ak-si-duhnt] Show IPA
an undesirable or unfortunate happening that occurs unintentionally and usually results in harm, injury, damage, or loss; casualty; mishap: automobile accidents.
Law. such a happening resulting in injury that is in no way the fault of the injured person for which compensation or indemnity is legally sought.
any event that happens unexpectedly, without a deliberate plan or cause.
chance; fortune; luck: I was there by accident.
a fortuitous circumstance, quality, or characteristic: an accident of birth.
Looking at definitions 1 and 3, I disagree that the term accident doesn't apply. The first definition even includes auto accidents, another type of vehicle to vehicle collision, as an example.
Your analogy to DUI is flawed because that is an act where someone knowingly takes an action that impairs their ability to drive and knows the risks to others involved when getting behind the wheel intoxicated.
It's applicable to some extent when somebody is texting, putting on make-up or whatever but many of these SMIDSYs are caused by people who fail to see a motorcycle due to how human physiology (vision processing in particular) works - or doesn't. (See above linked article.)
People also get killed in car accidents daily as well. Do you think somebody should start up MACA? (Mothers Against Car Accidents) Do you think legislators would respond and impose mandatory penalties for people who kill/maim others in auto accidents? Do you think prosecuting attorneys would decide to pursue it every time somebody killed somebody else in a car accident? I don't think either is a realistic expectation.
Riders are a relatively small minority in this country so the chances of legislators taking action with respect to motorcycle accidents are even less. Then throw in the fact that we, as riders, CHOOSE to ride a vehicle which leaves us very exposed.
Being a rider, I sure as heck don't want someone to take me (or any other rider) out in a SMIDSY but I recognize that it's a risk I choose to take every time I throw a leg over. Not saying that any rider deserves to get taken out in a SMIDSY or that the person who kills a rider isn't at fault, just acknowledging reality.