Look at this sentence: 1. "Mike said that he enjoys reading books."
Reading books is enjoyable for Mike, he likes to read books, it is a fact, something that won`t change.
But the sentence: 2. " Mike told his brother that he needed to talk to him."
Talking to his brother is a temporary situation, the moment he talks to his brother, the validity of the sentence disappears! And Mike no longer needs to talk to his brother, which means that the situation has changed.
However, in the first sentence, if Mike read a book , he will keep enjoying reading books.( unchangable situation).