Was asking myself the same thing. You have to fill on to enter most South American countries too and they barely look at it now that they have passport scanners.

I was asking myself the opposite question, about the U.S. smartphone app that lets you skip the passport control line, but saves NO time, because you still stand in line for customs, and how quickly you get to that line is determined by the baggage handling system.

@WGroleau wouldn't it save time if you only have hand luggage?

Possibly. But since my primary transportation is bicycle, I always have to wait for it in baggage claim. Last trip, though, the line I jumped wasn't very long. And then it took a few tries for the scanner to read the QR code the app generated. Also, the app doesn't work until you connect to the internet. And since the "free wifi" is such a joke in some airports, and non-existent in others, …

The US form is a customs form, and the officers do not ignore the customs information you write on it.

@phoog yes but why force you to fill it out if you have nothing to declare? And even if you do, why force you to fill out details which are already in your passport?

@JonathanReez inertia. It takes time and money to implement systems that remove the need for people to fill out the forms by hand.

immigration forms get thrown away right after you get your passport stamp Any evidence regarding that or just hearsay ? Secondly you haven't traveled to countries where they do read the landing card i.e. Australia, New Zealand and if caught lying prepare to pay a fine and confiscation of goods too. As far as I can tell the immigration officers usually completely ignore whatever details you wrote in those forms That generalization is wrong on so many levels. When I entered US and was carrying food, the officer did query what I was bringing in ? So not always do they ignore what is written.

I was flying to UK many times from mainland Europe and never had to fill out any form

@DumbCoder yes the US officers do look at the form, but only at the part where you declare things. Why not allow people to just go through without a form if they have nothing to declare? That's how it works in the Schengen area. And if you ask for a declaration, why force people to fill out the details that are already in their passport?

@kukis yes because you are an EU citizen :)

yes the US officers do look at the form, but only at the part where you declare things Again an erroneous generalization. How did you know the border agent didn't look at the whole form ?

@DumbCoder because they don't need to look at the parts which are in your passport. If I write I'm a US citizen in that form they wouldn't let me in without a visa, would they?

they don't need to look at the parts which are in your passport Another wrong assumption without any proof. If you look at the landing card for USA they don't ask your citizenship/visa status etc, more for declaring goods/money. Same for Australia and New Zealand too. Only UK is different. If I write I'm a US citizen in that form they wouldn't let me in without a visa, would they? Not sure what you are alluding to.

@DumbCoder the immigration agent scans your passport when you arrive. Hence they don't really need you to fill out your name, date of birth, etc.

@JonathanReez they check the data to make sure the form matches your passport. If you showed up with a passport that said "Jonathan Reez" and a form that said "Mickey Mouse", or indeed with a Russian passport and a form that said the passport has been issued by the USA, do you really think the officer wouldn't notice?

@phoog but again - they have your data right there on their computer once they've scanned your passport. Why fill it out by hand then? Or why not allow you to fill out a mobile declaration form (if its so important) and just have you scan a QR code at the machine/upload the form to DHS servers? :)

@JonathanReez they need the passport data on the piece of paper because the piece of paper is going into a file box somewhere, and it might be necessary at some later time to match it with the person who submitted it. The least expensive way to get that data onto the piece of paper is to get the traveler to put it there before appearing at the desk. The answer to your "why" questions is in my earlier comment: inertia, perhaps combined with a desire to allocate IT development resources to other priorities.