A favourite excuse is a perceived workload increase on the PM. That excuse is pure tosh and they know it.
The PM is now also responsible for updating the radios, heading bugs, CAB, FMC and MCP, checklist as well as trying to monitor what the ace next to him is up to. However in benign airports such as HNL, BNE, etc it should be no biggie so I agree with you there. LHR, LAX, JFK after a 12 plus hour flight maintaining the big picture is far more important, so I would not agree with you in those cases.
I would surmise that the biggest impediment to more pilots opting to leave everything in is FOQA, stable approach criteria and touchdown monitoring that is now prevalent in airlines, as well as ATC track/speed monitoring plus airport noise monitoring. To keep the skills up one must accept the occasional deviation as we are human pilots not dumb dutiful machines. However a few calls from the "Lord FOQA" or ATC report about a "deviation" or "noise bust" you understand that it just is not worth it!