"What gives are these just people who come in and just copy whatever they find and use it as a valid tree.... are people just copying whatever they see on another tree"
In a word - YES.
As to your concern about lazy people copying - sometimes the people who do this are clueless, and have no idea how to find actual records and documentation. At least, if they copied from what you had found and documented, their trees would be accurate to that extent (but don't hold your breath...)
This is widespread, rampant, and encouraged by Ancestry (through its "you don't need to know anything," and putting forward other members' trees as "sources" or "research"). You have to just do your own thing, and ignore what others do, IMO.