"You need to...."

Why do we tell someone "you need to...."?
Why do we talk about someone and say that he or she needs to do something?
There are two likely reasons. We think we know what's best for them or we want them to do something to our liking. Is it an observation, a judgement or a reflection of our own need?
I don't know about you but I'm not always very good at taking care of what I need to do for me. That's not anyone else's fault. Knowing that, it's not easy to hear someone say "you need to". I may agree with them, but I do wonder if it's an observation, a judgement of a reflection of their related needs. If I am not ready to do what they say I need to do, it stings.
Are we more likely to say "you need to" to a stranger or someone we know well? "You need to" can sound very harsh. It sounds more like a judgement than an observation. For example, if you see someone get out a car with a flat tire, you are most likely to say "Hey, you have a flat tire" and not say "you need to change that tire".
On the other hand, if we see a stranger with a cut on their forehead that appears dangerously in need of attention, we are more likely to say "you need to have that looked at". We want them to take us seriously. We add an emotional appeal.
And perhaps therein lies the answer to why we say "you need to..." So, is the need theirs or ours? About a month ago, I told someone that I've known all my life that "she needed to..." do something that I know she clearly does not want to do and likely won't do for, perhaps, the rest of her life. While I believe I'm right, I later regretted saying it. I know that I said it more for me than for her. I said it because I would like to be around her but avoid it because of her anger and bitterness. I regretted it because maybe I'm wrong about what she needs. Maybe she needs to be angry and bitter for a while longer. I said it because I feel helpless in easing her pain. I said it because I cannot help and it frustrates me. I said it more because of my feelings than hers.
Most of us don't want to see people we care about hurting. We want people around us to share our sense of wellness of some kind. If they share their pain with us, we will feel more compelled to tell them what we think they need to do. We may be right. But I'm hoping the next time I'll remove myself a bit. Perhaps next time I'll ask, "What do you think you need to do? Is there anything I can do to help you?"
That is something I need to do for me but I also believe it will serve them better as well.