ATC workload? Can't believe someone was actively watching that radar and failing to advise. Is VASAviation simulation accurate?
Perhaps the parallel runways at SFO so close that ATC are used to seeing traces almost on top of each other, hence lack of concern?
Is it just me or have there been rather a lot of incidents recently at SFO? Seem to be a number of factors making it one of the higher risk airports at the moment. What could be done to fix it?