I think it is vulgar and rude. I find some wedding lists totally unacceptable as well, especially those with gifts costing a minimum of £100! I won't name and shame, but one list wanted £100 for a salt and pepper grinder and some either poxy thing, a glass condiments tray, like the ones in restaurants.
I can understand people requesting nice bed linen and longterm useful household goods. I didn't have a wedding list, but I still received some wonderful useful gifts and some also had the forthought to include an 'exchange receipt' which most decent shops now provide.
I can also understand newly weds wanting a contribution towards their honeymoon but in that case, it should be done through one of those agencies.
My cousin did this. She sent out a flyer with the wedding invitations asking for donations/payments towards their honeymoon, via a travel agency.
A couple of months later, we received a lovely thank you card and a "round robin" type of letter as to what their honeymoon was like - although I have a fair idea; my cousin gave birth 9 months later!
It is the decorum that counts in such times, but nowadays no one cares about decorum. It is seen as snobish and old-fashioned, which to me, is the ultimate irony.