For me, if its just a ceremony and an excuse for people to have a party, I can't see the point. If you want to have a party, have a party - why drag the church into it? If its an event which is genuinely significant and which you are doing through deeply held belief, then I'm not sure that what people are wearing really matters. Well it wouldn't to me.
So.....would that be the same for a funeral?
You wouldnt mind if someone turned up to a funeral for a family member dressed in dog walking/decorating clothes or jeans and a scruffy t-shirt?
I wouldn't turn up like that myself, but no, I wouldn't mind if anyone else did. What does it signify? We are there to mark and mourn the death of a loved one - its just as possible to do that honestly and sincerely (which are the things that matter to me at such occasions) in jeans as it is in a suit.
What would upset me would be if someone turned up, however they were dressed, but really didn't care about why we were there, whether its a wedding, christening, funeral or whatever. Attitude and integrity are what demonstrate respect, not outward appearances. For me anyway.
But if anyone is going to an occasion of that sort where the people involved DO care about dress, well yes, it wouldn't be right not to comply with their wishes. I suppose the way to ensure there are no misunderstandings is to mention it when the event is organised.