Then there's the famous feeding of the cake to each other – and this is supposed to show love and commitment too, and of course if you'd like to read into this further it can be seen as helping each other out and being there for each other.
The classic wedding cake is what everyone expects and so you don't have the strong likelihood that you are leaving anyone out by choosing something more unusual that they can't eat. At the same time it echoes the bride's dress and is part of the whole paraphernalia of the wedding and part of the expectation. It is almost as though having a wedding without a classic cake is akin to having Christmas without a tree.