Originally Posted by
sdsearch
It's only because they lump carry-only people with people who check bags that you're not "sterile" after going through USA immigration on USA soil.
There are ways to clear immigration and stay airside, if you're carry-on only, in some airports overseas.
Is there any country that does not require passengers connecting between international flights to pass security screening? On more than one occasion when transferring at LHR, I had to undergo TSA style security screening even though I did not have any checked bags and did not go through immigration and customs.