The way a gift registry normally works is you make a list of all the things you want and people buy them for you.
The problem with that is you still have to shop. For me, shopping is the worst part. I hate having to go out and look at stuff and figure out which thing best meets my needs. The fact that other people are paying for it is very nearly negligible compared with the tedium of having to do the actual shopping.
If I had a gift registry, I'd want the opposite. I'd want to make a list of everything I need or want - simply describing it in words without having to provide any information on style or model or where to buy it - and as their present to me people would go out and shop for it. They wouldn't even have to buy it, I'd be happy to use my own money. It's the shopping that's the hard work.
Problem 1: There's nothing to stop people from just picking out any old thing without regard whether it meets my needs. For example, I want an desk chair that is ergonomically perfect for my body. When I mention this to people, they tell me the name of a store that sells desk chairs and suggest I go there and sit in some chairs. But that doesn't help me at all. I already know the way to get a desk chair is to go to stores and sit on chairs, and for me that's the difficult and annoying part. They're basically restating the problem as though it's a solution. And there's nothing to stop people from doing that with the reverse registry - not actually doing proper shopping, just naming a product that exists and declaring the job done.
Problem 2: I'm never going to be on the receiving end of a gift registry, so with this invention I'm just making my job harder.