My FMIL keeps relaying questions from her side of the family asking us if there are any gifts we need. We have a registry at Macy's (about 12 items left and all on the low cost side) and at Target (about 30 things left in a range of prices). If we needed something, we put it on the registry.
"Do you need wine glasses??" No, we've got plenty of wine glasses, that's why we didn't register for any.
Here's the thing, if someone wants to go off registry, good for them! We'll appreciate the generosity and figure out if we need to return it as a double later unbeknownst to them. But if you want to know what we want, we already spent HOURS crafting a registry of things we want/need. Sorry you are picking from less choices on the registry, but the wedding is 4 days away, so it is what it is.