I haven't found anything in a vase, but then I ignore most of them and am perfectly happy with that. I wouldn't go peering in every vase I passed in real life, though I could, so it makes sense to me that they're interactable but I don't interact with them. And if someone has put something good in some of them and I miss it, so be it!
It's also useful that we can interact with them to do things like block vents, though I guess they wouldn't need to be treated as containers for that.
