civix is a development tool. It generates code for extensions, providing a baseline for developers and hackers who want to improve and add onto CiviCRM.
civix generates a lot of code. Much of this code is educational; hopefully, some of it is even useful. But some parts of it are redundant or excessive. The excess bits don't matter much with a single extension. However, in practice, they are copied to almost every extension. Individually, these are small bits. Collectively, they add up.