Because you're driving a ton or so of machinery. Full stop. This is the whole BÁNH MÌ THITing point.fat and old wrote: Why should I be responsible for someone who makes no effort at all to help himself?
Had that been a small child, dog, cow or car door the result would have been the same.
Particularly if I take you at your word: that YOU did not see another road user, despite being close enough to need to pass him and travelling fast enough that you had to take evasive actions.
SMIDSY remains a cop-out for not paying attention; not being aware of the blind spots and/or driving too fast for the conditions.
*note that the legal system would have, as other posters have pointed out, blamed the victim for failing to meet all the regulations. And I'm a big fan of reflectors & bike lights. But you are supposed to have headlights and you supposed to be using them to spot hazards.