Trying to keep with MJ's question ...
Although I race 'cuz I love it, honestly, I do believe that I can design and make better bikes because I race, and race like a nut. I do have a better feel for what race bikes need to be able to do and what they must NOT do than those who don't. Racing is just different from other kinds of just as legitimate types of riding. Where I first noticed how racing helped me understand the requirements of real race frames was in my early days of racing on the track. I was one of the local sprinters, just a bit below the level of the national guys. When I was training with Leigh and Jerry, I realized that my track bike, with its generic mid 70s Paramount geometry simply didn't work right at the speeds that we were sprinting at. On most American tracks, holding the bike down in the corners was a real chore. The year I got 6th at the Nationals in Kenosha was the final straw. I couldn't hold the line between turn three and four to save my life. Granted Kenosha back them had a pretty bad transition between three and four, but it got me thinking about how I might change geometry to help racers. Maybe I could make a bike that racers wouldn't have to be conscious of, wouldn't have to fight to get it to go where they wanted. This is just one example, but the problems that come up in races where ALL problems will exhibit themselves have spurred me to figure out ways to solve them. So, yup, racing can improve the breed. Doesn't always happen, but it can. Helps?