The pros ride whatever bike their team's bike sponsor gives them and pays the team to ride. Cannondale sponsors the Cannondale-Garmin team at the top level of the sport, and thus they don't bother paying another top level team to ride their bikes. The same is true of Trek as there is only one pro tour team that rides Trek, namely the Trek Factory Racing team. By your reckoning, neither Trek nor Cannondale must be good since only one pro tour team rides their bikes.