Not all Ancestry users realise that there are advantages to uploading a private (but searchable) tree - even LostCousins members email me about this. So one cannot assume that people who haven't uploaded a tree don't have one, although I agree that this is often the case.
Why do people test if they're not researching their tree? In many cases because they were given the test as a gift, others because they believed the marketing. Some may aspire to research in the future, others may have no such plans.
Fortunately we all have more than enough matches with cousins who do have trees. That's why the strategies in the
Masterclass focus on those with linked trees, whether public or private, and ignore that the rest.
Obviously it's frustrating when one of our nearest matches has no tree and refuses to respond - in my case it's my closest match
and he has used an obviously false name (Gerald Wiley) which means that whilst I know what part of my tree he is in, I cannot identify who he is. But corresponding with him wouldn't help me to knock down any 'brick walls', so I don't get hung up about it.
Finally, it's important to bear in mind that people may not be receiving our messages. There are several large email providers who bounce emails that they, in their 'wisdom', determine are spam. Even worse, some put them into a 'black hole', so neither the sender nor the recipient is aware of what's going on. The best service is probably Gmail, but even they don't put all incoming mail in the user's Inbox or Spam folder - instead you have to look in the All Mail folder (and many Gmail users don't even know this exists).