The FAA acts on behalf of the US citizens, and because of reciprocal agreements, much of the world's aviation consumers. As such, all of those people have a right to expect an effective certification service. The FAA has delegated some of this service to specified employees of Boeing, who, in that role, act on behalf of the FAA. That topic merits discussion, as it is the basis of public confidence in an airplane which is compliant with the design standards.
This is the heart of it all. Governments establish regulators to ensure that their citizens have no more exposure to risk than is absolutely necessary. Companies buy aircraft on the basis that it will give them an economic advantage, and safety is central to that (or should be). Crews have every right to expect their company will give them a safe system of work within which to operate, and passengers expect to survive their travel experience.
We have certification, airworthiness and operating processes for good reasons, and there is inevitably an element of trust that runs throughout - trust that people will comply, for the benefit of all. The moment individuals or entities try to circumvent hurdles rather than clearing them, we are in trouble. And it is not just manufacturing in the frame here. How many times have we seen disasters where the investigation uncovers pilot training and qualifications that have been sharp-pencilled? People lie through laziness or self-interest but proper oversight should be a strong barrier against this. You could argue that the system failed to protect Lubitz and his Germanwings victims because there was inadequate oversight of his fitness to operate.
Add to this the global move towards Performance-Based Regulation and Oversight, with PBR/PBO being heralded as avoiding un-necessary costs to industry. The question is whether we have the balance right. If you subscribe to the argument that better oversight would have prevented the MAX scenario and the Germanwings event, it follows that you also agree the balance is not quite correct. I am not suggesting we should revert to the old compliance routine, but I think it is high time the aviation system took another look at PBO to ensure that 'Oversight' means appropriate 'Overwatch' rather than inappropriate 'Omission'.