That's the whole point, we have a lot of prestige involved we have told the media when things will happen, we in the boardroom are not prepared to look plonkers if things are late, and not prepared to allow the budget for full testing of say... The Hubble Space Telescope.. or the Large Hadron Collider. Shove it in the water and hope it floats.
And yes I know the arguments, engineers would test it to destruction and start again if they could.