Do not misunderstand here, not ALL fan fiction is necessarily great, just the well thought out ones where it actually looks like the writers put time and effort into it. It takes a special mind to write a good fanfic, and when that happens, they are pretty fun to read, especially if you like to obsess about certain characters or various fandoms. Here are four reasons why fan fiction is awesome:
1. They are Somewhat Easy to Write
If you think about it, fan fictions can be quite easy to write if you have your idea well thought out and planned. The world that the TV series, book, or movie inhabits is already set up for you. The characters, rules, philosophies, and way of life is already created for you to write about. It is very convenient if you really enjoy the certain genre the world your fandom exists in, and it is that fact that takes a lot of work: to come up with well written characters and worlds.
2. It's a Great Way to Obsess Over a Fandom
Like I said before, it's a way for fans to connect with their favorite characters and stories in the world, to create plot twists in the stories and to experiment with them, especially if you enjoy crossovers. OCs or original characters are a great example of this, where the writers can live through their character in a way. Another example are one-shots or reader x [insert favorite character here] type of fan fictions... They're a great way to obsess as long as the writer rates the maturity level on the fanfic properly or gives a warning and the OC isn't a Mary-Sue, a fan fiction term for a character who's cliche and just too perfect.
3. It's a Wonderful Way to Get in Involved in the Fandom's Community
When you're writing a fanfic you are writing to the audience that loves a fandom or a character just as much as you do! If you make your fanfic look appealing to read, people are bound to check it out. That means good grammar, spelling, complete sentences, etc.
4. It Can Be Used as Writing Practice
Writing fan fiction, if you put some time and effort into it, can be a great way to sharpen those writing skills. Not only that, you can get a lot of critiquing from it, and hopefully have it be mostly helpful. On sites like Wattpad and FanFiction.net you can get comments and reviews, along with Beta readers as well.