I am often called with only caller's call sign for my CQ. They send it only once. If the caller is right on my frequency and in time, I could guess I am called by him/her. The problem is that they are often a bit off my spot and are delayed starting calling me. It confuses me a lot. Nowadays, there are numerous pile ups (games if I could say) going on even away from the DX window. Pile up participants could be like those callers. Should I reply to them?
Another frustration about them is that they won't enjoy "tell me your story type" QSO. As soon as they give the routine items like report/name/QTH, they are always ready to quit. Actually, even if I should ask them about them, they ignore that or they won't seem to understand me. I haven't counted such callers yet. In my impression, they are up to 70 or 80% of the whole callers.
So far, operators enjoying conversation are sometimes in those callers. I am dubiously replying to them. But who knows I won't answer to such a caller any longer soon? I am actually inclined to feel going that way.
Please don't omit my call sign before giving yours when you call me.