Rec. specs and straps aren't exactly trendy, but since when has NFHS been concerned about whether or not what the kids are wearing is fashionable. I can see a situation in which a kid losing her glasses and another player stepping on the lens(es) and their feet come out from under them. It's not likely, but it's certainly more likely than the same thing happening if a bobby pin fell out of a player's hair. Isn't this why bobby pins and clips are forbidden? It is kind of hard to believe that there isn't a NFHS rule that specifically addresses glasses.
Regardless of whether or not the NFHS thinks it an important issue, the ultimate responsibility rests with the parents and coaches. My daughter wore rec specs while playing basketball, she didn't exactly like it, but she wore em. (And now we have some great ammunition ... errr, I mean pictures to show people)