In Chapter Nine of The Great Gatsby, why does Nick feel responsible for the funeral?
Nick is the first one that makes any calls regarding what had happened to Gatsby. Because he did so, every practical question or idea about the situation seemed to be referred to him. He notes that others just weren't around or available. Nick tried to connect with Daisy, but they were gone. He realizes that this came down to just him because no one else took interest in doing something about the fact that Gatsby was gone. It became his responsibility because no one else stepped up to take responsibility or even wanted the responsibility.
Then, he feels responsible to make sure that people attend because everyone should be honored in their death. He feels like it should be easy enough to find one person who cares. This is why he went to Wolfsheim. He thought if anyone, Wolfsheim would care. But Wolfsheim can't because he sees plenty of people die in his line of work and to get sensitive now would be a problem for him.
In Chapter Nine, Nick states that he feels as though he must "get somebody" for Gatsby's funeral. To understand the reason why, take a look at this quote from the chapter:
It grew upon me that I was responsible, because no one else was interested—interested, I mean, with that intense personal interest to which every one has some vague right at the end.
In other words, Nick feels responsible because he was, quite literally, Gatsby's only true friend. This is important since it suggests that those who appeared close to Gatsby were shallow and superficial. They were only interested in Gatsby when he was alive because of his reputation, his wealth, and his parties.
By claiming responsibility, then, Nick demonstrates that he is not like these other people. His interest in Gatsby was based on genuine affection and friendship. As such, he feels compelled to give Gatsby a proper funeral as a mark of his loyalty and respect.