That's been my experience. This winter the weather has been horrible in the northwest, and so several of my flights have been cancelled. And the airlines wouldn't give me anything since it was weather related. Whereas recently I volunteered to skip an overbooked flight, and ended up getting a free roundtrip ticket, meal vouchers, and a ticket on the next flight out.

Yeah, but why would Spirit's flight have been cancelled? It wasn't weather. I think they cancel due to underbooking. I guess they figure they'll pay for your ticket on a nicer airline, which should be worth something.