Whether it be a short film lasting three to fifteen minutes, or the more ridiculous idea to make a full feature film (80+ minutes). It just grows and festers in their creative mind until they just have to make the movie. It would be so simple to get a camera, have a couple friends chase each other around the woods with a large knife, and call it a movie. Don't forget to push the record button.
While the term independent film  has been warped over the years, there has always been a low budget world out there and that world has a large following and fanbase, too.
It’s not like you can’t see on screen that they didn’t have an overly bloated budget like some superhero or melancholy space opera film. It’s pretty damn obvious.
Independent filmmakers need to make a film people want to see, if they want to get any remuneration or potential future work. I've heard sequels are quite popular nowadays. Without a healthy  budget, these filmmakers have to be creative to make every penny count including effects work. This is why these films need word-of-mouth and positive reviews (online and in the real world) to help keep this style of filmmaking alive.
Check out a film festival and you'll see just how many people are out there making movie magic.
Help keep independent filmmaking going.
Go watch a movie at your local theater or find a film festival that fits your flavor. I promise you'll find one.