@elisto Standards naturally emerge, sure, but it's on the order of where to put things and what keywords to include.
However, there's nothing stopping personal style. Some people might want to cram details in the margin. Others might forego the details. Some people write big. Others write really really small. Some people might use too much ink and fill the paper with splotches. There's no shortage of ways to make a document less readable and inconsistent from its peers.
It also doesn't help that culturally, you could show off your intelligence by writing more. So you might prefer using sentences to say "I paid $X.00 amount to Y today, MM/DD/YYYY for {reason}" instead of having in the top left, "Notice of Payment", in the top right, the current date, and then in the center of the document an amount, a quick memo, and a signature. Which shows off more and which would be quicker to read?