I'm currently creating a tool that will allow users to configure SPAN ports on a Cisco switch, and I was going to implement a feature that would allow a user to create a VLAN and add ports to it so it can be set as a source for the SPAN port without having to configure it on command line. But I can't see a reason why a user would set up a VLAN on a local session, it would make more sense to me if they simply just assigned the ports they want to monitor instead of assigning them to a VLAN and then assigning the VLAN as the source.
Can someone explain to me why I would use a VLAN, or is my statement above correct, and there is no need to set up a VLAN?