Cactus, i think i said i didn't know anyone who went to funerals to support the mourners, not that people didn't think they were going to support them or that there were peopel who went solely to support them (in my family and group we only go if we knew them, to grieve our specific relationship with the deceased). Or at least that's what i meant.
But i do question the idea of 'support' in general. I think people want to feel like they are supporting and helping people so they go. But to me i would feel no support by that, in fact i'd feel a bit insulted. I would feel no support by someone who didn't even know the person being present while i grieved. It would feel horribly ghoulish, morbid and awkward to me. I would definitely tell someone not to come if they said they wanted to. Having a stranger to the deceased there would make me feel way more distress (unless they were to perform a specific task). i don't think it is rude to say politely 'no thank you for offering but please don't come along, we only want people who knew the deceased there', surely people should be able to mourn in their own way. And if your intention is to 'support' the bereaved then surely in this circumstance not going is doing more to do that than turning up where you will make them feel awkward? Or should people feel the need to be social and polite even on their darkest days?
As offensive as everyone thinks not going is, and me saying it's 'for show', that's how i feel inside and i find it equally offensive the other way round. If someone said, do you need any help? would you like me to be there? I would find that nice and supportive, i would decline and say no though, but appreciate the offer. But people just expecting to come because they think they are supporting me and therefore making themselves feel good by thinking they are helping is presumptuous.
Also at our funerals we have no hymns or even much of a service. Just very short really. We don't need to pack out churches or to make hymns sound good. We just cry a lot in a very small chapel while someone says something very brief.
Allguns - did you feel comfort by them being there seeing you like that? I do hope so. Personally i would hate it. It would impede my grieving. I hope you are starting to feel better now 
I think it's important to remember funerals are for those grieving and you should follow their cues. If they want you there then go, if they don't, then don't feel offended. It is such a personal thing and no one should be made to deal with it in a way they feel uncomfortable with.
As an aside, i knew a few Irish (i mention this because i do know its the culture to attend) people who would go to everyone and anyones funeral, people would try to politely put them off, but they just carried on, they rode rough shod over the wishes of those actually grieving because, i suppose, it was their culture and they couldn't really comprehend why we all felt squirmy and awkward about it. (They also used to eat all the food and drink all the booze and try to get everyone to sing Irish songs and bang on about how great funerals were back in Ireland
- but that's a separate issue - they obviously missed home and were trying to make what was happening something more familiar for them) We used to have to keep funerals a secret! 