TLDR: They likely care, just a lil dumb
I feel ya, i attempted a lot in my mid teens (didnt have a lot to work w, had to use really obscure methods and my survival instincts kicked in every time) Every attempt resulted in me waking up the next morning and having to go to school (a few times i actually tried AT school in the washroom) Not a single person ever noticed my passed out body, how i'd go missing for hours frequently, etc...
I know it's wild for everyone here to think about, but some people actually love living and wouldn't do anything to hurt themselves. These are often the same people who don't think bad things could happen to them until it does. I think a combination of these attitudes leads them to think that they'll never lose a friend, etc... to suicide because they don't think about the fact that some people legitimately want to die, and they don't notice any of the signs because they've never experienced it for themselves.
I highly doubt they want you dead and would likely be devastated thinking back to all the red flags after you passed, unfortunately they just dont know how to express it beforehand.