Aviation history is filled with examples of why flexible structures are best.
Some (quite a lot actually) years ago the Royal Navy used RR Nimbus engines in their Wasps. The combustion chambers were found to be flexing, so RR added strengthening webs to them. The webs stopped the flexing, but the stresses caused the webs to crack. The cracks ran into the chamber walls and pieces started to fall out. A small problem had been turned into a much bigger one. A cleverly designed modification was then added to reduce the size of the webs, so that the chambers could flex a little bit without cracking.
I would be more concerned flying in an aircraft in which the wings didn't flex. Brittle failures give no warning, just drop that glass your holding and you will see what I mean.