Well it all depends on how you were taught penmanship. Used to be the school system had a very rigid set of rules for writing in script. Now its not taught as much. I am just a year older than Obama so we probably learned to write under those same rules.
Lefties were always taught to curl there hands around like Obama is shown doing in that pic so they could get that proper slant the writing teacher wanted you to have.
Actually, the reason lefties write like that is:
1. so we can see what we are writing
2. So our hand doesn’t smear the ink.