Originally Posted by PeteHski

You can definitely argue in favour of more vertical frame compliance. In fact many manufacturers already have. That's why we have super thin seat-stays, D-shaped seat posts, IsoSpeed, Futureshock, etc. Wider tyres and lower pressures have arguably made frame compliance much less critical in very recent years, but still I'd rather not have a bone-shaking stiff frame for riding on our pot-holed roads. CF goodness can give you vertical compliance and high lateral stiffness at the same time.