[yodon]

Most English language handwriting has an up-and-to-the-right tilt. Architects will frequently adopt a precisely vertical style but it tends to feel cold and impersonal (or perhaps just unfamiliar as most writing does have a bit of slant to it). I suspect it's a bit like the serif vs sans serif debate. People generally prefer the look of sans serif fonts but they read farther into and retain contents better when the font has serifs (first measured in the 1950's and first discussed broadly in Ogilvy On Advertising, the book that most of Mad Men season one's plot points were based on). Straight up and down seems like it would be best, but for whatever reason hundreds of years of practice have retained that small angle as the preferred style.