I listen pretty much all the time on com 2 unless I'm using it to check weather. I've heard a lot of ELT's (always report them and have learned how to get a rough bearing), some 'aircraft xyz center is looking for you on', and the 'On Guard' guards.
The reason I try to always listen is I've heard several intercepts and two real maydays. I was the only one that heard one of the maydays. That guy lost his prop. He ended up landing it safely in a field but he was far enough in the sticks that he may have been there a while if I hadn't of been able to report his position. The other didn't turn out as well. It was reported by someone else but the pilot that made the call didn't make it.
I carry a PLB and between that, my cell, and my ELT, I'd hope I could let someone know I had a survivable problem but it's nice to also hope someone is listening if I ever have to make that call or my ELT goes off.
Gary