Which ones?
"Prank them with an undecryptable random file" https://news.ycombinator.com/item?id=19834934 and "prank them with 20,000 goatse images" https://news.ycombinator.com/item?id=19837896 as they can get you back by seizing your electronics. Of course, those sound like jokes not serious suggestions.
"Have it remotely locked by an administrator" https://news.ycombinator.com/item?id=19835097 as they won't understand that technical mumbo-jumbo and will just seize the laptop.
"Have a hidden dual-boot system" https://news.ycombinator.com/item?id=19836135 as if they take a disk image and spot it, they'll be particularly suspicious of you.
Some posters also think "Send your encrypted laptop by mail" https://news.ycombinator.com/item?id=19835019 is not good advice.
Because most people don't have the technical know how, or desire to spend the effort to ensure that the data they _are_ bringing across the border is safe to disclose.
Even elsewhere in the comments here is a long debate about the "safe" way to deliver data across borders, some of which are actually terrible ideas.
Yes, theoretically, people could avoid bringing any sensitive data physically across the border, but most do anyways and I bet you do too.