If you look at their "feedback left for others" you can get a better idea. Some sellers only leave feedback for others sellers, and some used to give feedback to buyers in the past but haven't left fb for buyers for a long time. I have noticed this sometimes. I think some big sellers don't even know that feedback for buyers can be automatic after they leave positive fb, as I have seen some give fb a bit at random, just to show they leave fb for buyers maybe, but they don't leave fb for everyone. I have seen some buyers leave really great feedback, but it was those who left "normal" feedback who also got feedback. A bit strange, that's why I thought maybe some sellers leave fb at random because they sell a lot and leaving manual fb is a lot of work if they don't know it can be automatic.