I got into fanfiction reading and writing back around 1993. Almost as soon as I got an internet connection, I went looking for more information on my then-favorite TV show and found a lot of other fans of about my age. Turns out they were all over the world (though mostly in the US). We chatted about the show, passed around behind-the-scenes info, visited the studio several times (groups of us), praised and complained about the show, and eventually in there somewherestarted writing fanfic.
Some of it was very good (surprising the authors), and, even with editorial help, some was... not -- BUT! The main reason everyone wrote was because they loved of the show. The paid, official writers were constrained by the network and turnaround time, and, just as bad, they sometimes seemed not to have the same love of the material that we did (and many still do). Writing for the show was just a job for the official writers. But
they got paid, and sometimes it didn't seem to matter what kind of cr@p they were being paid to write. Fanfic writers don't get paid, and I salute
them because it takes a whole lot of courage to struggle to write something
and then put it on the internet for everybody to see. That's love, and that's what fanfic writers have for their subject.
Also, addressing copyright, all the fanfic authors I know of very quickly started each story giving due credit to all the original rights holders as well as the actors and notice of any episodes that might be mentioned in the stories.