How many illegal immigrants have their passports and are willing to risk flying with them? I'm more talking about the mindset of illegally entering a country and then having the expectation that I can do anything there, anyway. Like in my Norway example, I can't imagine just walking to an airport and expecting everything to work out when I just boated into a random part of the country illegally. Is this a US idea that that should be expected to work? I don't have the perspective to know, so I'm asking.
Living in the Netherlands, I haven't had to show ID to any government agent when flying to another country in the Schengen area in at least ten years (and I fly quite often). If I don't check in online then I am sometime asked to show it at check-in. And sometimes I have to show it at the gate, but the people there are only eyeballing it to make sure the name matches the boarding pass.
Note that I do often have to show ID on the return flight. Each country (and probably airport) has its own procedures.