I remember this discussion from a while ago. Some people think the gift doesn't need an acknowledgement, and some want to be thanked for gifts.
I definitely want to be thanked. A few years ago I went to a wedding, and gave money instead of a gift, as the couple had requested. They boasted later that their wedding hadn't cost them anything, it was all paid for by parents and parents-in-law. No one was thanked for their contribution.
The same couple have recently had their first child and I sent a box of gifts. They included hand knitted items, a pram toy and two bought outfits. I haven't even heard that they have received them, and certainly no thanks. I sent it over three weeks ago so I am annoyed at the lack of good manners.