I don't buy this. Everyone had different handwriting in the good old days, and this did not make grading unfair.
They used something called word count.
I suspect it actually did make grading unfair. Having pretty handwriting probably got you a better grade. Although, arguably it also made the writing more valuable, for instance if someone were ever going to write things like business letters.
Similarly, I was in college when word processing was introduced, and I think that turning in lengthy and typographically perfect term papers probably boosted my GPA. Thanks to doing lots of programming, I could sling text like nobody's business.
The reason for these rules is not related to printing. These rules are in place to enable fair grading:
- fixed font styling and page margins allow proper comparison of paper lengths (e.g. a student might try to use a bigger font size or bigger margins to get around a "submit 3 pages of text on issue xxx")
- fixed line height requirements allow teachers to print out the submitted document and annotate it - the resulting prints and the correction marks are usually archived to make disputes easier