It is a very valid question Richo.
For a fat pleb like me, you wouldn't think it would make a difference, but it does. For the elite blokes, it would make a huge difference.
I went from a lower end aluminium bike to a full carbon bike and straight away went faster. A combination of lighter and stiffer and more aero. There was about 2.5 to 2kgs difference in weight, and for me, that is about a 2% drop in total weight. For the lighter guys, the percentage is much higher.
It is the combine affect of all these little things that really adds up. I am sure I could go quicker with a better set of wheels. But the thing that would make me faster than all of these things is if I dropped 10 kgs.
![Smile :)](./images/smilies/smile.gif)
Sarc ; my second favourite type of gasm.