[DockerCompose] Why copying source in local?

[Tudyx]

• In production environment we copy the sources without mounting. I understand that we need the sources to run the server but we don't need to modify them
• In local environment we copy and mount the sources. I understand that we need the sources to run the server and we need to modify them. Why are we copying the sources, just by mounting we could have the same effect, didn't we?

If someone please could help me, it's seems that i miss something here.