Is it necessary?

Is it really necessary to make your own mistakes? Is it really worth it?
If you look at a person acting a certain way and you do not think positively about that action then why would you not take lesson out of it? Why would you want to experience it for yourself?
I recall an incident from my childhood when I was about 9-10 years of age and I was taking a walk with my dad. We saw a car rush by splashing water from a puddle all over the sidewalk. I made a comment about how inconsiderate the guy was to act like that and my dad said, "if you speak like that about him, would you not want to refrain from doing the same thing?" I treasure that moment for life and it taught me the most valuable lesson.

I could understand that mindset when a person is in his teens, unaware of the surrounding world and is not fully aware of the consequences. However, this mentality of "make your OWN mistakes" makes little sense to me when a person is over his teen years. Does it not defeat the whole argument of learning from mistakes of others? I mean, is that not one of the most compelling argument for studying History?
Makes me feel how people, special young minds, have biases in certain areas of life. A principle is applicable to one aspect and considered ridiculous in others.
I recognize the notion of individualism and how one each one has his own set of principles, morals and beliefs but these principles just need to be universal, atleast to a person himself.