There are situations where you can really use the largest bag on the planet as checked luggage but the number of times you would actually use it is slim to none. So, that's when you travel with a cheap rollup duffle bag inside your luggage or personal item, like the one below to bring back a bunch of stuff from international traveling. Or to use to for long term stays. No need in spending a lot of extra money for a large check-in piece of luggage that won't get routine use.