There used to be a glass plant near the town where I grew up.

The bottles don't just get washed and refilled. They're melted down and recast, just like aluminum. But the process is much less energy intensive.

Aluminum oxide (the natural form of aluminum as it reacts with the atmosphere) just so happens to have an extremely high melting point. Aluminum smelters must use all three of pressure, heat, and electrolysis to get the oxygen to burn off and liquefy the aluminum. Glass and even steel need only heat. I don't know what the final environmental impact is, but the energy input at the point of smelting is much higher for aluminum.