A jerk posted on Armslist that people listing guns with super low round counts were scamming liars. I expect many sellers are like me. Have too many guns and a small number of favorites to shoot. Some safe queens go for years without firing. Also I bet I'm not alone in buying two, as with the CZs I listed, to see which I prefer, then selling the other. And lastly, I like putting together custom ARs. If I have 6 similar, I'm not going to shoot them equally. Typically one would go to the range regularly, one occaisonally, and the others stay unfired or nearly so.
Lord knows there are plenty of scammers on Armslist, but that kind of broad brush indictment really gets me steamed.