Racing bikes are quite light and are only as strong as they have to be for racing. Racing bikes do not even have the mounts on the frame to install racks.

I have three touring bikes, one is rated for 30 to 35 kg of weight capacity not counting the weight of the rider, one is rated at 60 kg of weight capacity not counting the weight of the rider, and the third has no weight rating.

Look at how many spokes are on each wheel on a racing bike and then look at how many spokes are on a touring bike wheel, you will see the difference.