It is generally not so much about the fact that rasterisation couldn't do the things. It probably could, but it would most likely need several rendering passes and all kinds of dirty tricks to accomplish things that depend on nonlocal effects.
Its simply easier to think in terms of allong path of a ray than per layer of total effect. Meaning its also easier to implement. Tracing is also significantly faster than multiple layers of rerendering of the scene once complexity needs become high enough.
But obviously theres no thing that you technically could not do with rasterisation because its essentially just a different way of doing the same thing. Its just that some things are not feasible that way.