Residential building code is 24" high sills, so most older houses will still be fine. Tempered glass is now required if the sills are lower than 18". But things that are not to current code are generally grandfathered in if they were legal when they were built. There’s no requirement to correct it, unless specific laws are passed. (For example after a horrific dormitory fire in NJ dormitories were required to have sprinklers.) That said, I think colleges and universities can and should do sometimes do more than the minimum that code requires.
Those window guards weren’t required in NYC until Eric Clapton’s son ran through an open window to his death in 1991. I’m sure they’ve save plenty of lives since.