Why do people make fangames?

[yamina-chan]

so then why don't they just come up with their own ideas? the end if western civilization comes when creativity dies.

I have no idea what the second half of this is supposed to mean, so I will focus on the first half; the question.
Why don't they just come up with their own ideas? Because in that situation, they don't want to. They want make a tribute to something they love verry much and share that love with others. That does not necessary rule out the possibility to never make a game that its not a fangame. Of course, some people are really bad at this. Like, really bad. But you will find that with original games as well. I'll just say Ankluas.
But there are also those who are good at what they do and if they decide to use that skill to make a fangame, so be it.
Of course there is no guarante that it will turn out to be good or liked by other fans. But again, that can happen with original material as well. Think of Remakes of games. Or Movies. Or adapting books to movies. Sometimes it turns out fantastic, and sometimes not so much.
That can happen from the "official" side as much as it can from the "Fan" side.
Also, as someone who writes original storys as well as fanfictions, besids teh challenge factor that I allready talked about, sometimes you have really no say in the matter of what you work on. What I mean by that is that sometimes you'll just get an idea. Uncalled for, not purposely. You just have this idea suddenly, and it is strong. You think about it for a moment, and you find it to be really good and interesting. And possible to work with. And then you'll get excited and want to explore that idea further, work with it and you want to find out what the finall result will be like.
Those ideas won't leave you alone. It might take a while to get it done, but those ideas stay. And you simply have to work with them.
About 90% of the storys on my own list came up this way. I write about things that I'd never thought I'd write about simply because I had an idea that wouldn't leave me allone.
You can't chose what ideas you have, you just have them.

-I know, I'm saying you a lot. I speek from personal experience only but I belive this is the same with many other people out there.