Text form is required for easy consumption by humans. Computers also process code in text form quite easily. Therefore generated code should be generated in the form that is easiest to generate and easiest to consume by computers, and that is very often readable text.

And when you generate code, the code generation process itself often needs to be debugged - by humans. It's very, very useful if the generated code is human readable so humans can detect problems in the code generation process. Someone has to write the code to generate code, after all. It doesn't happen out of thin air.