Tacky, and I've been in that situation. Most couples I know have lived together before they got married or one or both owned a home or at least had a well-furnished apartment already and didn't really "need" things per se. And yet they've had traditional showers where they've managed to register for some items. There are plenty of home items that don't last forever and need to be replaced, like linens and towels. Even if someone has china already (perhaps it's been inherited, which was my situation) most couples can use some nice everyday dishes or some extra serving pieces, kitchen gadgets, outdoor grilling accessories, etc.
And if they're looking to purchase a home, there are plenty of things that they don't have already. When my shower invites went out, the host included a card that said that we were registered at Crate & Barrel, Sears (because I have older relatives who I knew wouldn't shop at C&B) & Home Depot (yes they have a registry!) and that gift cards were welcome. We had just bought a house, had consolidated two apartments into one small home and had more stuff than space but knew that we needed practical home stuff so we registered for some things like gardening tools, grill accessories, and tools (really!) in addition to table linens, serving pieces, and traditional items. We had some duplicate gifts from Sears that we were able to return and buy the table saw that we really needed (we didn't register for that LOL) and we got some gift cards that helped with our renovation and new homeowner expenses.
No matter the reason, IMO showering people with money is just poor form. However, I will say that it seems that what is and isn't acceptable in terms of showers varies greatly from region to region so I would pay more attention to the answers that come from others who live in your area. It is not something that would be done here.