Odd immigration visa questions

I have a visa in my passport, permitting me to enter the United States (I needed it for a job but never got the chance to use it).

I seem to recall answering some questions on the application form like ‘Do you intend to enter the United States of America to carry out terrorist activities?’.

What is the purpose of such questions? - surely no terrorist is going to answer yes, and if you do catch a terrorist, the fact that he lied on paper is going to be a relatively minor matter, isn’t it?

It’s so no one can blame the Customs Service for not asking you if you plan to carry out any terrorist activities when you come here and blow something up.

It’s so that they can deport you for lying in your visa application (as a less drastic alternative to jailing you) if you’re engaged in behaviour they don’t like.

It’s like the question: “did anyone else pack your suitcase for you?” (Yeah - my mother - because I’m crap at folding).

I mean if someone is being paid a few thousand dollars to carry in a bag for some shady character, they’re hardly going to admit it to the check-in lady…

My understanding is they ask the “did someone else pack your suitcase” thing so you can’t try to evade prosecution (if something evil, most likely drugs, is found there) by saying “I didn’t put it there”.

If you reply yes, they’ll ask you whether you were present when it was packed. If you say yes, they can nail you if something illegal is in the suitcase (because you knew about it). If you say no, maybe you’re more likely to be checked and questioned in detail, I don’t know.

I’ve wondered about the terroritst activities thing myself. I suppose it’s legal trickery that serves a certain purpose, bot something useful in its own right (surely it won’t detect a terrorist), similar to the mail fraud thing discussed here recently.