I think part of the reason they didn't put something such as the death of a parent on there is because it's quite possible a child may have had a strong support system to help them cope with that.
Childhood stresses are generally divided into three categories: positive stress, tolerable stress, and toxic stress. Positive stress is "good" stress, such as starting school for the first time. It encourages learning and growth. Tolerable stress is stress that's harder to handle, but can be managed with good support. (Studies on resilience in children have demonstrated that the single most important factor in determine a child's resilience as the result of a stressful event was the continuous presence of a supportive caregiver.) Toxic stress is stress that can't be managed well - examples include abuse and parental substance use.
There is substantial evidence now that exposure to toxic stress, especially in the first three years of life, actually alters the way a child's brain is wired. While it is possible to correct some of these effects, it becomes more difficult over time. One of the major issues is that many of these toxic stressors don't occur in isolation (for example, a child may be abused because the parent has a substance use disorder), so the effect is cumulative.
If you (general) want to learn more about this topic, you might google "The Brain Story". There is actually an entire certification program you can take online, to learn more about the effects of ACEs and toxic stress on children's development and risk for problems. I have completed the certification as I thought it might be useful to my teaching (and there are some pieces I bring in when teaching pediatric nursing). It's very interesting.