After Gatsby's death, Nick, his only true friend, arranges for the funeral and tries desperately to get other people who knew Gatsby to come and show their respects. The only ones who show up are Henry Gatz, Gatsby's father, the owl-eyed man, who Nick had met in the library at one of Gatsby's parties, the minister and a few servants. None of the hundreds of guests who had attended Gatsby's parties bothered to come, which is significant because it shows that while he was alive they were very happy to drink his liquor, dance to his music and enjoy his benevolence but now that he is dead, they have no more use for him. Even Gatsby's business partner, Meyer Wolfsheim, doesn't attend and his words to Nick were:
"Let us learn to show our friendship for a man when he is alive and not after he is dead."
It is more likely that Wolfsheim wants to hide his association with Gatsby, especially after the scandal surrounding the death. Most upsetting to Nick is that Daisy does not come to the funeral, nor does she bother to call. She and Tom had quickly left the country for an extended trip abroad, in order to avoid any repercussions regarding Myrtle Wilson's death.
In the end, Gatsby's funeral, unlike his parties, was a somber and lonely affair. No one showed up because Gatsby hadn't really cultivated friendships or personal relationships with anyone, except for Nick and of course, Daisy.