I think this entirely depends on previous experience. If you've been there five times and every time there were tons of leftovers being sent home with people, and possibly a shortage of old plates and giveaway tupperware, bringing your own box and avoiding the dance of "how do I get this plate back to these folks" seems pretty sensible to me? I've been in situations where bringing a box would have been/was helpful to the host. (Especially in a family like mine where ordering the kind of take-out that comes in reusable boxes just isn't much of a thing.)

If it's the second visit and there's no actual reason to assume this would make the host's life easier, and this just comes out of nowhere, then it will look really odd, I agree.