Here's why:
* Simple predicates are the verbs in a sentence that tell what the subject does or is. They can be single words or verb phrases.
* "Means" is a verb, but it needs an object to complete its meaning. For example, you would say: "This book *means* a lot to me." In this sentence, "means" is the verb, but "a lot to me" is the object.
Think of it this way:
* Simple predicate: The action or state of being.
* Means: Requires something to be the "means" to something else.
In short, "means" can be part of a simple predicate, but it is not a simple predicate on its own.