Because what it actually protects is rights, rights of the end user.
You of course know this, but you instead choose to endlessly harp on the meaning of the word 'freedom'.
Licencing your code under GPL grants the recipient of any binary in which your code is included a specific set of rights.
These rights include the right to the source code should the recipient want it.
This particular right makes GPL very interesting for many developers as they can release code, and then as recipients of modifications of that code, get access to those modifications in source code form and thus gain improvements to their original code.
You of course know this, but you instead choose to endlessly harp on the meaning of the word 'freedom'.
Licencing your code under GPL grants the recipient of any binary in which your code is included a specific set of rights.
These rights include the right to the source code should the recipient want it.
This particular right makes GPL very interesting for many developers as they can release code, and then as recipients of modifications of that code, get access to those modifications in source code form and thus gain improvements to their original code.