Now here's a interesting speculation.
Let us suppose for a moment that pilots only see 10% of the traffic, so then there is only a 1% chance that both pilots see each other.
So now most pilots think they are 10x better than average, because 90% of the time they see "the traffic", and evade, but the other aircraft carries on S&L, obviously "not keeping a good lookout like I do".
Most pilots will be too modest to actually say that, (unless they are glider pilots, of course
), they will just think it!
I suspect this is similar to the "logic" that makes 80% of car drivers believe they are better than average.
There is a serious point here. If the typical pilot is mostly seeing traffic without being seen, one could indeed conclude that most traffic is missed.