They do not check but they ask for it. You got off like most as they did not have a reason to ask further, however when you travel a lot to any of those, you still might get unlucky-ish. I for one got asked for detailed itenary and names of friends I will visit (because I was visiting friends) at the US and CA borders. And at the Thai border for that matter. But then again I travel a lot; when I go for business (once or twice a month) to UK (very strict even though I am a regular and from the EU) & China (where I never had any issues or questions asked), I often add on a trip somewhere else just for fun. The US is mostly quite easy, UK the hardest of all (very annoying).