Some states keep them sealed, but a lot make them available under FOIL requests. Obviously you do have to keep in mind the privacy of the surviving family, but even so the argument that it's not a public record is a tough one to make. After all, it's a written report prepared by what is typically an elected official, running a governmental agency, all being funded by taxpayer dollars. Together, that's the basic formula for a public record. Plus, obviously there are some public policy arguments to be made in support, too, such as minimizing hearsay and speculation, educating the public, and some First Amendment issues in higher profile cases.I'm not sold on the idea that the general public should be privy to this type info, even though I understand the points you make about why the autopsy info was made public. My thought is that common decency would keep this info about Lutz private to not add to his family's grief. But evidently that's not the top priority in situations like this.
The bigger fight has been not over the reports themselves, but over autopsy photos. Florida had a big back-and-forth over that with Dale Earnhardt's death several years ago, and that resulted in some legislation being passed and a lot of litigation.