I think one factor here are the wives. It was considered as great honor to have MS or elder husband, so they did everything necessary to encourage their lazy husbands to reach for those positions. Nowadays I would guess it is more appreciated to have certain amount of trips abroad and acceptable standard of living, so today they encourage their husbands to achieve those goals first and the spiritual ones then if more energy is left.
You know by nature we men are little bit lazy and like rolling the responsibility to our wives (consider the things Adam told about his wife).
CP