Yeah, my last sentence sounds wrong in hindsight. Should have said "That is just not a traumatic thing to me at all" or "That was not a traumatic thing at all.
I absolutely agree that a line should be drawn where you expect children to prematurely... well... mature and be parents/adults.
In my case, I was 12 or so and my sister was 6, so we both came home from school and were alone until our parents got home from work. They never expected me to make her do things or something. When we hadn't done our homework when they got home, the consequence was that the homework needed to be done still and we couldn't go out and play. That's it. My job was to make sure my sister got a warm meal (reheated; pre-cooked by my parents) and basically didn'T die. They asked us to do certain things while they were away (vacuum the living room or something) but they never really made a fuss when we failed to do it. They just made us do it later then.