Think of a typical sprint stage. It's long and flat and the tactics are to manage the breakaway, the sprint teams organize a chase, catch the breakaway and set up leadouts for the final sprint. Now mix in 'bents. When that happens, the 'bents are the breakaways and they never get caught and there is no sprint. That's because on long flat courses standard bikes are at a distinct disadvantage. The only advantage left to standard frames would be in climbing. If you love bike racing, you don't want to see 'bents on the pro circuit.