Grew up as a youngster in the shadow of Muroc (Edwards) and can remember many of the early test flights in the 1950's.
Aeroplanes were pranged left, right and center, yet the programs continued.
My Dad worked for Douglas for a very long time and some of these test pilots were dinner guests on a regular basis (as was Donald Douglas Sr). They ALL knew the dangers involved, yet never lost sight of the objective.
In many cases, no matter how carefully the program has been managed....s--t happens.