I never use ancestry trees except maybe to get a tip. Or, occasionally I go there to get a lead on a maiden name of a married woman. I put the url of the page and the maiden name in a fact called "Links to Maiden name". I never put it in a Name Fact until I have it supported from somewhere.
Why would anyone who subscribes to the databases use the trees? Not only are the they inaccurate and full of garbage, but as you say, they are unsourced. I'd much rather do research in the databases. That's the fun of this genealogy activity is finding out relationships and solving puzzles on people from the past - not copying trees.