Ditto.
If I do my own air arrangements to get to the ship, then I know I am taking a risk of not only cancellation (what if it were like the Navigator that has the fire and cancelled TWO cruises) but mechanical issues, weather related issues, (if I can't get there they won't hold the ship for me) so I have to make a back up plan. If that means I don't sail but lost my airfare, then that was my choice. What if they had to use an alternative port then who should pay? If I use my air, then I am on my own!
When we flew to Alaska there were some RSSC pax that were delayed from Florida because of weather issues and their connection was late. We were supposed to sail from Vancouver at 6. They held the ship until 3AM for those passengers. If you did your own air, you'd have had to get your own transportation to the ship. Same situation with Shore excursions. If you are late, the mass market lines leave no matter what. RSSC might wait a reasonable time but you'd better be prepared.