I was basically forced to buy one many many years ago when cases with no optical drive bays first came on the market. The motherboard I got with that build had the drivers on a CD, and that included network drivers. I had no secondary PC to download them with. I suppose I could have used my phone, but back then the internet wasn't built for phones very well, and I remember it being a pain in the ass. Since then I have used it quite a few times. It's always been a great thing to have just in case I need it.