Additional cancellation fee on a nonrefundable plane ticket: is there any disadvantage to just not showing up?

I bought a ticket through justfly.com, but I might need to cancel it now. I was informed that the ticket is nonrefundable, which is fine--I expected this. I was also told that there would be an additional cancellation fee. This seems strange to me. Is there any reason that I couldn't just not cancel the ticket to avoid the fee, and then simply not show up for my flight?