I suspect there are a few reasons the market for cycling is bigger:
- The importance of being able to see is much higher. Before I got Lasik, I would just take my glasses off when running. I could see well enough to stay on the path and avoid other runners or walkers. Being able to see and react quickly is just more important on the bike.
- Even normal-sighted cyclists frequently wear glasses for UV/sun protection and as a wind screen.