I think the standard psycho-therapeutic "tell them how it makes you feel" advice applies here and accounts for the difference. It's one thing to give unsolicited advice to someone. It's quite another to tell a close friend "Look, I need to tell you something important because I care about you. When you start telling me all the ways I should change to be a 'better person', it really makes me feel bad, and makes me not want to hang around you. It certainly doesn't motivate me to actually make any of your suggested changes."

I don't really think unsolicited advice is even that bad usually. if you see someone struggling with a task and offer a good tip, they usually appreciate it. when someone starts venting about a problem, they are (implicitly) asking for something other than advice: usually just a kind ear. this is basically the worst moment to start offering advice.