Also I just ride my bike too, quite a bit actually. I lift simply because I enjoy it and it makes me feel better about my body than I would doing aerobic exercise alone. Twice a week, one upper/abs and (recently) one lower/abs.
From a training perspective, lifting makes me less prone to overuse injuries and acute injuries from crashes. I'm sure it also increases my 1-5s power output numbers, but those are rarely the limiters in the kind of racing I do where the last few laps are fast and a sprint can be 10s or longer.