As you may well have noticed from the chapter on hacking a custom lighting model within the Standard shader, once you start to build up functionality upon functionality and need to support many different platforms with very different capabilities, the complexity of shader code can get very high, very fast.
A characteristic that most shader systems share is the need to be flexible, while the language itself doesn’t really provide much flexibility. Unity is experimenting with writing shaders in C#, so this may change in the future. ...
