I think the difference between the Cheeki Rifiki and flight MH 370 is that the crew of the yacht will have known that, however competent and invincible they felt, sailing in those seas would always be inherently risky. Passengers on a commercial airline, on the other hand, would be expecting to arrive safely at their destination.
For the crew of a transatlantic yacht to drown is shocking and tragic, but something we know might happen. For a commercial flight to vanish into thin air is shocking, tragic and incomprehensible.With so little support you can understand the families histrionics.