That's a good point. As far as I'm concerned, it's for two reasons,
1. You desperately want that person to know TTATT. You care about them, and wish to rescue them from themselves.
2. You like to prove that you have the superior knowledge and intellect.
We all want our loved ones to have the best life they can have. Reason #1 is altruistic.
If it's #2, then you best take a look in the mirror. It's unfortunate that those who wish to show their superior knowledge, don't seem to own any mirrors. xx