These can include, but are not limited to: violence and trauma in one's community and family, lack of reliable parents or positive role models in one's community, childhood economic pressure towards physical survival and meeting basic day-to-day needs.
These are all things that individuals born into poverty in the US face at disproportionate levels, and they can have a negative effect on motivation. We generally don't fault people for the very harsh circumstances they are born into.
But the fact remains, which sucks, but still.
Where do we draw the line? I was attacked by a dog when I was a child which was very violent and traumatic for me. I also grew up "are we going to eat tonight" poor. Do I qualify?
We learned that people need vitamin C to prevent scurvy; now we have government policies and cultural norms that make sure that every child gets enough vitamin C.
As our scientific understanding of brain development grows, we'll (hopefully) develop norms and policies to make sure kids get what they need there too. You can see today the early stages of that process with respect to exercise, and more recently, sleep.
Definitely. It's sad that these outside factors influence something so important, but that doesn't change the fact that some people are motivated and some are not, does it?