IMHO - I don't think it's about "not caring". I think it's so stressful that the only thing addicts/alcoholics can do is stick their collective heads in the sand and pretend it's not happening.
My sister left me to tell her children that our father, their grandfather had cancer. She didn't tell them for weeks, but they figured it out on their own. When I found out what was happening you could have peeled me off the ceiling (it was unclear when my sister's ex found out). One of them actually started crying herself to sleep in the middle of the night because she was so stressed out about it. The "funny" thing about it was that he had a type of cancer that was highly curable, so when I told them what was happening they were actually relieved.
It was so unnecessary. It's frankly just easier, not to mention more responsible, not to expect anything from my sister at all. I won't make the same mistake again.