Precision in landing was important because NASA chose a relatively tight area for Curiosity's arrival: The Gale Crater, which contains an 18, 000-foot high mountain about 7.5 miles south of the landing site.
It was a precision job, like landing on the Moon, as the team lowered into Erte Ale and recorded the first ever 3D laser scan of this remarkable volcano.
When to let a pilot know his landing is aborted requires precision timing--turn him away too soon and, given the nature of aerodynamics, the plane will smash into the deck or the water.