I had a cousin that committed suicide by jumping into a quarry. I was 12. My mom and I went to the wake, and when we got to the body, the casket was closed from the chest down. But it was glaringly obvious that he had been at least partially decapitated, because his head was just kind of awkwardly shoved on. They tried their best, but apparently you can't make that look natural.
So, years later as an adult, I started wondering why in the world my mom would let me see that. So I asked her. It turned out to actually be a thing that no one in the family spoke about openly. My mom didn't know he would look like that, and neither did anyone else.
After my cousin died, he was transported to a funeral home. My aunt insisted on an open casket, which the funeral home refused. It somehow escalated to the point that my aunt hired another funeral home on the condition they have a viewing.
No one except my aunt knew any of this until after the wake. So people start showing up, view the body, and see that he doesn't have a neck and was decapitated. And it isn't like you can go around and say "fyi - the dead guy is all jacked up from jumping into a quarry and you really shouldn't look."