There's also the matter of fatigue. Aluminum, for example, is far stronger by weight than steel, but it is subject to fatigue in which microscopic cracks accumulate. These can often compromise virtually all the strength of a component before they're visible to casual observation (they can be detected via microscopy, x-ray, and sonic analysis).

I've had several aluminum components fail on me, suddenly, on bicycles. The experience is ... not particularly heartening.

Glass is similarly not known for being highly flexible or self-healing. Among the benefits of asphalt is that it has little internal structure and does reflow to an extent (more so under hot weather, often to the point of creating a hazard). Given the punishment taken by roads, this is a significant benefit.