Originally Posted by
robow
Actually there probably is none but titanium never rusts and will always stay shiny and should you run into Magneto on a bad day, you can still ride away.
There are practical reasons as well. Steel is a strong material but, let's be honest, it's heavy. Titanium has about the same strength of steel but half the weight. The fact that the material is relatively inert also makes it attractive. Steel's only advantage is that it is cheap.