Don't you think it's pretty arrogant to tell people what to do in life?

Typically. Unless someone is being a jackass and ruining things for others, most people can figure out their own way of doing things. They don't need someone else to impose their values on them, especially if they don't really know the person. Just because something works for one person doesn't mean it'll work for everyone else. Different people face different challenges and have different opportunities from each other. Telling someone what to do is pretty much useless unless they've been in the exact same conditions as that other person