One thing that’s changed is that flags used to be generally made of cotton, and likely to mildew or rot if left out overnight to often. Now they are often nylon, which is much more resistant to getting damp from evening dew.
The rules aren’t completely arbitrary, even if elements are arbitrary.
Well, nobody from Ohio, anyway.
Hey, at least the average Buckeye can read instructions! Could be worse! 
I am reasonably certain that when Americans who own flags need to fold them, the vast majority just do it any way that seems convenient.
The Proper Care Of The Flag Militia mainly exists in the form of occasional outraged letters-to-the-editor writers.