这里不用定冠词与 there be 句式有关，因为 there be 句式作为存在句，其后接的名词通常是非特指的。比如通常说 There are some people in the room. 而不说 There are the people in the room. 当然这说的是通常用法，不包括特殊用法，比如 There are the people who want to see you. 可视为 The people who want to see are there 的倒装形式。