They age out. So if there is no activity (responses or pushes) they just fade away like old soldiers. This keeps ten year old ads for window felt or something from clogging up the board after they sold nine or more years back.
I agree, but this site as a hole does not get much attention. Kinda low volume compared to other sites I'm on. But still a good site. I've made friends and offered advice to a lot of Impala guys. Every now and then I sell them some parts.