The main reasoning behind this is that an analysis of approach incidents/accidents over many years showed that in 75% of cases the Captain was flying the aircraft when these incidents/accidents occurred. So why not get the FO to the fly the approach?
Obviously the captains were all sub-standard and poorly trained otherwise why would they crash. Perhaps swapping seats would have fixed this appalling record? One presumes that all of the accidents referred to here were non-automatic approaches because aircraft do not normally crash on fully automatic approaches and landings