Well, a lot do, LOL. But IMHO, just talking about this ONE situation in the OP, it sounds like the couples' immediate family can't even come. I don't know what fun that would be.
For some, that would be really fun

I am not a fan of DW but not because I think the b&g are being selfish but because it is inevitable that someone will have a problem when a family member declines the invitation because they will expect you to be there. It doesn't have to be the b&g in order for family relationships to be strained over a DW wedding.
Having said that, I think a couple can plan whatever wedding they want if that is what makes them happy. It IS their day and they are asking that you come share it with them, if you can
