I understand what you are saying and I agree that there are many unprofessional sellers on eBay. In fact, I would suggest in my 10+ years experience, most sellers are unprofessional. That said, what I and most buyers care about is good service. I pay promptly and I expect the seller to deliver promptly and safely - and, I don't really care how unprofessional they are - this is eBay after all.
The other important point that should be made, most sellers are subject to, subordinate to the eBay system. Frankly. the eBay system has not been seller friendly. I.e. - if you buy something you pay for it or its not yours. Ebay lets buyers fiddle around and pay at their leisure sometimes days or a week or more later - that is not right plain and simple. So, what is a seller to do? You start out by asking nicely, then you plead and then you demand. Unfortunately, within the eBay system, buyers can do as they dam well please.