I couldn't agree more with you. It disgusts me when I look for some information on someone's tree, hoping that I have found a solution to some tricky problem - and suddenly I notice that their tree has something like THIRTY THOUSAND people on it!!!
I then immediately realise that they have been adding EVERYTHING they have found without checking it out in any way at all. ...I check out a few things on their tree and sure enough the mistakes are GLARINGLY OBVIOUS.
They usually have duplications galore; they have obviously added every single "hint" that Ancestry has ever offered them.
What this means is that others copy their mistakes and these mistakes are copied for years onto other trees until the truth becomes completely buried. ...One tree had my grandfather as having died in Chile, and he had never even been out of the UK in his life. I was at his funeral here in Scotland and emailed the owner of the tree. They didn't even respond!
I NEVER copy automatically, and assume that the majority don't either. To keep a tree right, you definitely need to spend money, and I have done that. In fact, folk are always dipping into my tree to take the images of actual certificates I have attached to my tree as proof.
Glad you pointed this out.
P.S. On the other hand, there are also some trees with similar ancestors to my own which have been trendously helpful. But these are the ones that have copies of certificates or sources of each bit of information, usually attached to profiles on their trees, which can easily be checked out. PROOF is what it is all about.
Sorry for going on a bit...