I fly all over the world with the altimeter set on 1013.25 most of the time. The altitude source is from a static source fed via an air data computer (the standby altimeter is a traditional device and shows errors of around 400-500 feet at FL300+). With MNPS over large areas of the world, we cross opposite direction traffic at a closing speed of 1,000kts and as we pass, the TCAS display shows them exactly 1000' above or below. Occasionally the radio altimeter blips as they go under and that shows a separation of 1,000' so the method of using a static source with 1013.25 set via an air data computer is pretty consistent with airlines all over the world. It works very well so why change?