I'm left-handed and grew up writing English. Except in the cases that I take special care to hold my hand somewhat awkwardly off the page, virtually everything I've ever written has some amount of smudging. I have vivid memories of my graphite-coated hand in primary school. In addition, it's harder to see the flow of the word; your hand covers up everything but the last letter or two.

It's clearly something that impacts different people in different ways.