And, if you come right down to it, the bulk of costs comes down to cultural/family expectations for a traditional formal wedding with a couple hundred of your closest friends of the sort I used to work part-time for a (old-line Main Line Philadelphia) caterer as a teenager.
I've attended a wide gamut of weddings over the years. Some are in the above vein, others are much more informal affairs, still others make the wedding a small family affair and have a bigger casual party as a separate event.
Sure. But I'd argue that's heavily flavored by cultural expectations in many/most cases.
Put another way: If the norm was to have a casual catered party/BBQ at your (or a friend's/relative's) house for a wedding, how many people would consider planning a $50K reception and dinner?
I've attended a wide gamut of weddings over the years. Some are in the above vein, others are much more informal affairs, still others make the wedding a small family affair and have a bigger casual party as a separate event.