For me it’s the paranoia surrounding webcams. People outright refuse to own one and I understand, until they go on and on about how they’re being spied. Here’s the secret - unplug the damn thing when you think you won’t use it or haven’t used it in a while.
They, whoever it is, can’t really spy on you on something that’s already off and unplugged!
Awk, sed, and grep.
You might have a different type of person in mind than other commenters. Most commenters had such people in mind who won’t install a password manager or an ad-blocker, or won’t hard reboot their Windows unless supervised. Having said that, I don’t think that even if you had technical people in mind this fits the question. They tend to take substantial more effort to learn and use effectively than the scope set by the original question. I thought this question was for little things that have a quick, lasting, and substantial effect. Learning awk and sed is a different thing entirely, I think of those more as productivity tools you can invest in mastering, and pay off in the long run.
mind expanding on what these solve?
Awk is a helps you do any kind of processing of semi structured text data.
Sed is a stream editor which lets you edit a file using commands. Which is tedious until you need to replace something in a bunch if files or make very specific edits across a large number of files.
Grep is just find pattern in text file.