It actually takes explicit training and practice, as it goes against every social habit and "instinct" we have developed throughout our entire adult lives.
A big part of the lawyers job is to question people. Their stories fell apart pretty quickly.
Once I got quizzed when boarding ElAl flights. They have well trained interrogators. It turns out a complicated life story and ADHD method of story telling doesn’t make them happy. A lot of “I said X because the full story is way too complicated, so here’s the full version” ;)
People think they can stand up to it but it’s hard when it’s someone whose full time job is exposing fake stories.
I actually rehearse now, because police in the USA are so corrupt and unreliable.
Something along the lines of "I know you are just doing your job, but, respectfully, I must consult with my attorney before answering any questions."
Then (to their dismay and annoyance) I repeat the exact same thing over and over again when they inevitably ask me other, follow up questions, trying to work around my initial refusal. (It's so disrespectful, as well as illegal, for them to keep going at that point.)
I have also semi-successfully appealed their FOIA denials covering the incident.
It has resulted in the sexual assault of some of my traveling companions by US CBP (full and thorough body search, simply as punishment for remaining silent). CBP is lousy with criminal pigs.
You can't refuse to answer questions when entering most countries you aren't a citizen of, if you wish to be permitted entry.