That’s mostly because the UCI has very strict rules about bicycle design. They banned recumbent bikes very early in the history of the sport; more recently they

That’s mostly because the UCI has very strict rules about bicycle design. They banned recumbent bikes very early in the history of the sport; more recently they banned Graeme Obree’s “superman” position and other changes to the geometry of a normal upright. http://www.wolfgang-menn.de/superpos.htm http://www.wolfgang-menn.de/superpos.htm https://www.bikeradar.com/features/top-five-banned-tech-the-pros-cant-have-video-2/ https://www.bikeradar.com/features/top-five-banned-tech-the-... Check out Mike Burrows for some interesting bike designs. Check out the Battle Mountain speed records for what the highest performance bikes look like.