Not all written notes are created equal. Notes written by great minds can be worth millions, while those written by the rest of us may not worth the paper they are written on.
While what we write may not worth much, we cannot say that no one reads what we write — many of our writings have been read by others (usually by teachers who mark our written work on assignments or exams). When we hand over our writing to others, they have to figure out how we write each letter so that they can find out what we write. So in some way, we all have done some form of encryption without even knowing what encryption is.
With the proliferation of computers, more and more people are "writing" using a keyboard rather than a pen or pencil. Teachers always lament that some of their students written work is illegible. However, that number may be growing as students today may not have to actually write outside the classroom. In the fututre, teaching writing may require teachers to actually teach students how to "write" (with pen and paper, rather than typing).
Our writing is like our fingerprints — no two persons write in exactly the same manner (at least that is what I believe). Our writing is literally our signature. Some have even claimed that a person's writing is a reflection of the writer's personality and that we can find out what a person is like by examining the person's writings.
Trying to determine a person's characterisics from one's writing in an inexact science. Some can claim that if one's written words are small in size, that means the person is timid, a shallow person, a miser, while someone else can consider the same person to be environmentally-conscious and efficient (since one is able to put more information in the same amount of space). Likewise, someone can consider a person's writing to be messy, while others may consider the same person's writing to be from the hands of a professional (anyone who has read a doctor's writings knows exactly what I mean).
Some have also claimed that we can find out someone's characteristics by the kind of writing tools one uses. For example, someone who uses black pens a majortiy of the time may have different personalities compared to someone who mainly uses blue pens or pencils. Since I usually write my assignments and exams using pencils only, I can considered as someone who is mistake-prone, someone who often has second thoughts and cannot make up his mind (okay, those are accurate descrptions, but I better stop before this becomes another rant about my shortcomings). While we may be able to find out a personality trait or two about someone from one's penmanship, examining the writing utensils alone may not yield much about someone's personalities, since there is likely no single characteristic that, say, all blue pen users have in common.
I may be making too much of a fuss over something minor (again), but our writing is a way for us to tell the world what we think, what ideas do we have, and what we are like. I am sure many people would consider those to be quite important, even if only a few others care about what we write.