I don't mean this in a snarky way, but it's "not about you", it's about supporting and showing solidarity with the bereaved. You don't have to know someone very well to feel sympathy and want to show it. Funerals are for the living, not the dead. When my mother died the lady from next door came to her funeral, and she hardly knew her, and my father was very moved that she had thought to come, and thanked her.
It depends on the person. When the rabbi at my grandmother's funeral mis-stated her name, it bothered me that he didn't know her well enough to know her correct name, even though I knew he was doing his best to be helpful.
Then again, in general I am the type of person that would feel better with the support of a few very close friends than with that of many acquaintances, or even strangers. At a funeral of a loved one, I would want to be surrounded by people with whom I could talk about the deceased. I don't care about filling seats.
You are right that it's about the living. For me, that means having the opportunity to share you thoughts about and experiences with the deceased.
Either way, I would want someone come to a funeral to express their true feelings, not because thef felt oblligated to.