Not weird at all. We have a couple large but collapsible duffels that sometimes get stuffed into other bags if we know we're bringing back more than we departed with. Usually our clothes go into the duffels and whatever we're bringing back goes into the more durable luggage.

I've also checked empty wine cases on trips where we know we'll be bringing back wine. Now that airlines charge most passengers for checked bags, the airline-approved shipping cases have gotten a lot harder to find, even in places like Napa where they used to be available at any liquor store, vineyard, or package supply store. So we keep reusing ones we already have.