Can someone explain the appeal of second chance romance?

So I'm aro-ace (maybe relevant), but I do enjoy reading romance in fiction. I have my preferences as do we all, but I just cannot understand the second-chance romance trope. You're telling me one or both of these people have not moved on in 10, 20, 30, 40, 50 years? I'm supposed to believe that? I just don't get it. Maybe it's an aro-ace thing.