I'm with FB. The quest to save weight often pushes the envelope of material strength, eliminating any overkill in the design. This works fine until you subject the bike to something beyond what it was intended for. I've got a 1990s butted chrome-moly hybrid frame for the early 1990s that is overbuilt by today's standards but has held up to a couple of significant crashes and numerous lesser insults as a mixed use bike (winter, gravel grinder, etc) over several years. It's been bunny hopped, taken through rock gardens and off small drops by a 230# rider and I have absolutely no concern over this frame failing catastrophically. That said, it weighs significantly more than many higher-end modern butted cro-mo frames and way more than CF.

Lightness and durability have an inverse relationship. For any given material, the less material you use, the less force it takes to cause failure. Design can compensate to some degree and maximize the material's potential but the reality is that you give up durability to save weight.