Anonymous wrote:I didn't know this.
Does anybody know why this is the rule? I find it strange.
My guess is that it is because a lot of people's travel plans change after they go. Some people who are traveling to visit family or for business have to extend their stay due to health issues, family issues, work extensions, etc. Visas expire with passports and it probably saves the state department a lot of time and money to ensure that passports are valid for possible extensions. Although many people come back when they plan to, there are probably enough people who stay for a few extra days or weeks to cause quite a lot of issues for US embassies and the state department that they have this rule in place to ensure that any temporary extension is still covered.