It's about "moving the cheese". Most people are creaturea of habit, when you move their cheese it forces them to change their habits and instills panic due to fear of the unknown. More so if the person affected isn't tech savvy. They are afraid they won't be able to do what they did before, they are afraid they'll make some new mistake that will have disastrous consequences, they are afraid of being embarrassed with making some novice blunder that will cause everyone to laugh at them, etc.

For these folks changing their browser, even a little bit would be like you or I walking into the bathroom and finding the toilet paper replaced with 3 seashells. You can get past that moment of panic with some coaching but some people don't like to be helped so there may or may not be anything you can do.

My philosophy: if you're getting tasked with being the family IT department, lay down some rules: they use what you suggest or they don't get support.

http://en.m.wikipedia.org/wiki/Who_Moved_My_Cheese

It is "unsafe" for the would-be helper to help people who aren't asking/paying for help and who don't understand the difference between a easily changed default setting and installed spyware.

With such people, you never know when they will simultaneously accuse you of "breaking" their computer and remove your access to said computer so that whatever you've done that they believe "breaks" the computer indeed becomes "permanent" and is something they can be permanently pissed at you for.