While it would be nice if NFHS made their rules public and free, it wouldn't change much with the average fan. Various leagues and levels have had their rule and case books available for years and I wouldn't say those fans are any more knowledgeable rule wise than before. Reality is the average person isn't going to read a rulebook if they have a question about a rule. If a had a nickel for everytime I heard an announcer screw up a NCAA v. NBA/NFL...well...I'd have a whole bunch of nickels. 😉
As a sidenote, the NFL just NOW made their rule and case book available...before they went the NFHS route and could only buy the rulebook (at least readily...there were PDF copies out there that weren't officially released).