Anonymous wrote:I do my best to never. I guess this is looked down on in some frequent travel communities because of the extra time it takes to load and unload the plane.
Two other reasons:
1. Increases risk of issues on your trip- losing stuff, needing to wait, replace it, etc..
More importantly:
2. Makes you much better able to switch flights if something goes wrong. A lot of times if a different flight is leaving in 20 minutes they can't move your checked bags that fast, but if you didn't check anything you can get on. This has been key in getting home close to on schedule a couple times over the years when there was bad weather or mechanical issues.