Let's say your friend has a really bad habit. They're making a poor lifestyle choice or they're being socially insensitive to the world without even realizing it.
Shouldn't we, as their friends, be the ones telling them to quit it? Or at least help them understand the perception the world has of their action?
But, no. We don't. Because...we're their friends, and we don't want them to get mad at us. After all, it might be awkward. But if we can't be honest with our friends, who else is going to do it?