Real world example to help you understand:

Some of the source code for our projects is generated from Math Lab models. If we didn't push the source code generated from those models, building would require having Math Lab and the code generation tools installed. These are both very expensive, so the company, understandably, wants to only provide it to the developers who actually do the modeling.

Other reasons for pushing generated code include the use of custom tools to generate the code. Sometimes such tools are difficult to support. Other times, they must be kept private for various reasons.