And if you do not want to prospect your network?
Not everyone wants to write to their connections. In your campaign exclusions, an option prevents contacting your first-degree connections when they arrive another way, for example through search, an import or a competitor's post. People who react to your own posts or send you an invitation remain possible prospects, since they came to you.
If you turn the source on, the reverse is true: your network becomes a regular pool, walked every day, without ever touching the conversations you already have.