@scottalanmiller If you ever have a client that has both the office line, and a direct extension, you can find a need for 2 lines. Sometimes they want to call out as the office, but other times they want to dial out as their direct line DID.
Don't you normally just do that with a single line but use a code (or a button with a code?) If you use two lines, it messes with the ability to see if you are on the phone or not, because your main line remains free, even when you are on the phone. It's pretty crappy from a switchboard perspective, let me tell you