Posties get new frames every year. As for not seeing Kestrels in the TdF (this applies to any frame, actually): you may very well have seen one painted with another company's logo. The teams have sponsors and have to ride that company's bike, or one painted to look like it. Same goes for other gear. Lance's TT helmet is actually a proprietary design owned by him. However, it says Giro since Giro is his helmet sponsor.