这个变化和动词本身有关。很多动词都有自己的使用形式，可以看作习惯用法和搭配。如：keep sb + adj 可以看作keep 的习惯用法，这里一般不用to be. 但是：Parents want us to be safe. 这里的to be 可以省略。请看外刊例句：

1. My parents of course, wanted me safe and secure, but they also wanted me to stay where they could watch me and for me to be just like them.

2. They wanted me safe, and I wanted the same thing for them.

make 后也一般直接加形容词，不用be 动词。但当强调强迫的意思时，可以用be + 形容词。如：Did she do it so because that was her way to make him be really loving?

你提到的 The family rules help us know how to be safe. 这里的to be safe 和上面其他句的用法不属于同类，它和前面的动词无关。这是不定式和疑问词how搭配构成名词结构的用法。如：罗素的一篇文章名字就是：How to grow old.

因此，对于学英语的人，特别是初学者，何以解忧？唯有勤查词典，多看多记忆。