I understand what Toots is saying, though. I like CluelessBride's take on things. But for better or worse (no pun intended), there are families and communities in which this is so ingrained that even if everyone is perfectly polite about it, it will seem strange, to themselves and to others, if guests who are able to don't give cash gifts at least as large as a reaonable estimate of the cost of their "plate."
That doesn't mean that guests have to do it or that couples can demand it. It doesn't mean that etiquette requires it. The closest analogy that comes to mind is how giving a "thing" gift in a community where cash is the near-universal gift isn't a violation of etiquette but nevertheless seems unusual to people.
It just means that it is unrealistic to pretend that it won't feel to the givers, recipients, or anyone else like a deviation from the norm. Of course it would still be rude for anyone to complain or to criticize. But you can't stop people from feeling what they feel in terms of appropriateness, cheapness, and generosity, and those feelings will be based on what they are used to doing and seeing. And many givers want -- even though etiquette doesn't require it - to feel like they are doing what is customary, or want to give a generous gift in light of the recipients' community, even if it isn't their own. I think that is why Toots was stressing that this plays out from the givers' end, not the recipients'. Is that right?
Never ever from the recipients end.
It's the desire by the giver for the recipient to receive more than they are having to spend.
I went to the catered wedding of my friends' son. Because we were family friends she invited not just my husband and I but our entire family--so, five people total. My sons were not in a position to bring gifts, so this fell to me and my husband. Giving them $50 or something I paid $50 for when they were likely spending over $150 just to host us left me in the position of feeling that I had just cost the couple $100 when my goal was to make sure that they got something from us.
I gave them a cash gift of twice what I thought we cost them. Did they spend that money paying for flowers or a dress? I don't know. It's not really any of my business at that point. But, from my end, when I know roughly how much a dinner buffet featuring roast beef and an open bar costs, I wanted to make sure that what I gave them was over and above what they likely paid to host us.
For me, it goes to reciprocation. Sure, when someone hosts me for dinner at their house, I can reciprocate that. But, I am unlikely to ever be inviting these people to a formal catered event. If I don't cover my plate and more, I don't feel that I am living up to my social obligation of reciprocation because there just won't be an opportunity for it.
If I go out to a wedding and get a fine meal and free drinks that otherwise would have cost me x number of dollars, I don't feel comfortable about. I feel like I am profiting at their expense, and this is the most important part--because I can afford to pay my own way. I can afford to give over and above.
There have been times in my life when I could barely afford a gift and it didn't make me uncomfortable to attend and accept a level of hospitality that I could not reciprocate. But, that's not the case anymore.