aerospace is operating at the absolute limit of what can be asked of known materials science

And an unexpected transient load or heat flux can easily exceed material limits, or materials can have flaws. The ability to qualify the materials, components and processes for aerospace use is an achievement in itself.

Exactly this. It is relatively easy to make something mechanical more safe provided you have have a significant material buffer. Rocket abhors additional material weight so everything has to run with a limited buffer space for safety.