I think the lack of trees can be down to reasons for people testing.
As someone's said, it might be because they *have* to open an account on Ancestry and haven't got a tree themselves as they're testing to help a relative.
I think also there's people who just want to find out their ethnicity, and really aren't bothered about who their 3 x gt-grandparents were!
I originally tested with FTDNA, then did a test with Ancestry when it was on special offer. I have been frustrated by the lack of trees myself, but also by people sending me emails where they blast a load of their relatives names at me and demand to know how we're related. I don't know! Look at the tree - I've supplied it for a reason.
It's especially annoying when they've looked at my tree, then try to bend the facts presented in it to fit some random theory they have. "You've got the surname [blah] in your tree, but you're wrong, it should be [blah] which is the name of my [insert distant ancestor here], because we match at [insert genetic distance here] and that's the only way it fits into my tree." Because they don't get that the genetic distance presented by the test might not actually be correct, and they don't seem to appreciate that I might have spent years researching that family in detail, through multiple kinds of document. It gets in the way of looking for matches in a sensible manner. Arrghhh!