One problem could be that they are still young and still learning how to communicate properly, but it is difficult to learn how exactly to communicate when you are growing up. So, if they have something they would like to say, and that they need to tell an adult about, it is a lot more difficult for them to communicate what they need to than it is for someone who knows how to communicate and talk very well to.
Another problem they have is that they are at a higher risk of passing away/having severe complications if they get a disease. If an adult winds up getting a serious infection/virus/illness, they tend to be able to fight it off and be fine after a while of recuperation, but small children are not as developed as teens or adults are, so they have higher risks of getting serious complications or dying from even seemingly minor illnesses.
One more problem that preschool-aged children could have is just a lack of knowledge about the world in general. They don’t know things about the world, as they have not yet lived long enough to be able to comprehend those things. So, this results in them being more at risk of putting themselves in dangerous situations and getting themselves hurt, simply because they do not know what they are doing at that age.
I hope that this helps!
