All the Paperwork
Keeping things in the cloud? No, way. Boomers would much rather print out everything, even if it is 100 pages front and back. Conservation isn't an ideal that Boomers grew up with, so they don't see how wasteful paper is.
You can be sure to find their bills, important paperwork, and other paper products shoved into a messy box in their kitchen. You'll probably find papers that are years old, too, because they like to save things like that "just in case."