The thing these gimme brides and grooms forget (or maybe not) is that the money collecting "cultural traditions" predate bridal showers, gift registries, engagement parties, and even giving gifts at the wedding. Way back when these games started, whatever cash was collected during the reception was what they got instead of gifts, not in addition to them.
I wonder how many of today's happy, grabby couples would still cling so tightly to these traditions if they had to give up everything else?