Why Drivers nearly don't miss cyclists

Drivers always look far forward up the road not at the near things they have already accounted for. It's simply too late to deal with hazards when they are already upon them.

Having seen the cyclist very early and having planned their pass, once alongside, the cyclist is now a past event and the attention is now further up the road and especially for opposing traffic. The objective, to pass the cyclist without striking them, has been achieved. However the cyclist is bound to feel unnerved and insecure if the pass is only a matter of inches. That doesn't automatically mean dangerous driving, it is how one feels when being passed by big heavy machines on the move. That is the brain simply telling you you're in danger and asking 'what am I doing here?'