Simply saying that blame may be apportioned. Certainly, a four-wheeler driver may CAUSE an accident, but can they necessarily be BLAMED for it, when the trucker could have, by employing defensive driving, have avoided the accident.
For example, let's assume an ice-covered freeway. Traffic is moving at around 70 km/hr, and there is a junction 1 kilometre ahead. You are overtaking me, and think you may want to leave the freeway at that junction. Realizing that the freeway is icy, you pull in front of me to ensure that you are in the right hand lane as early as possible. The gap between our vehicles is now too small to be considered safe, so what should I do? At this point, I have no idea that you are intending to leave the freeway, and may slow down even more, and you have no idea what the safe stopping distance of my 63 tonne vehicle is, but you are not the professional, and you cannot, and should not, be expected to know.
Here, we can go one of two ways. Either I slow down to the point where I am maintaining a safe distance between us, actually anticipating the junction and the fact that you may want to slow down even more to use the exit lane, or I can reason that it was your fault that the gap is too small, and that you can take your chances.
I will slow down. You will slow down further, and, realizing that this is, in fact, your junction, you will indicate and pull over into the exit lane. At no time will you realize that I took evasive action, read your potential actions and was aware that you would slow down even before you knew that yourself. You should, in fact, never have realized that my truck existed once you had passed it.
The alternative is frightening. I decide not to employ defensive driving. I continue at my previous speed, and when you slow down for your junction, the gap closes. Now I'm driving dangerously close, and do not have full control of the situation. I blast the air horns, and start shouting at the useless four-wheeler who has caused this situation. It's anyone's guess how this situation plays out. You could end up dead, I could end up off the road while you carry on, shaking your head at the lunatic trucker. There are several possible outcomes, none of them good, and all I had to do was slow down and maintain my following distance.