I like when movies, books, games and other media create a world of their own with rules about how that world is working. And I hate when they break with their internal consistency.
That's why I love this place: people realize that they want to have an internally consistent world and that people might think they are breaking with their internal consistency. And others help in spotting these "problems" and helping authors of any kind to come up with ideas that fit into their world.
I love reading about the different ideas people have and seeing the level of detail people put into their work. The reason I ended up with an account on WorldBuilding.SE, which is the first site on the SE-network where I had an account, was the Anatomically Correct Series.
In the beginning I asked a few questions and tried to answer some things, too. Later I realized that most of my answers and questions don't really meet the quality standards that I would love to see on the site and posting stuff became rarer. Together with the following points this leads to my last answer being written on 2nd of February and my last question being asked on 13th of April. So I haven't really posted anything in roughly half a year.
After some time I realized that I can contribute to the site by editing posts. I may not be a native speaker and my english is far from perfect, but I can still spot quite a few typos and typical grammatical problems. I like to feel that helping others by checking their grammar and making sure that their questions are well-received by the community is a good way of contributing, too. Even if it doesn't award reputation once you cross the 2k mark, which was important for me to edit faster without having people approve my edits first.
Another way to help others is to give some feedback in the Sandbox and I think this is a great feature and the existence of the Sandbox shows that the community of this site cares about helping people post good questions instead of just closing everything as some people think.
I also love to check out the chat. There are a lot of weird and funny conversations going on regularly. I tend to have a tab with the chat open most of the time and regularly checking if something interesting happened.
All in all, I am more of a reader, than a writer. And there's a lot of interesting stuff to read and learn on this site.