Here's why:
* Imperative sentences give commands or requests. They tell someone to do something.
* Question marks indicate a question. They ask for information.
Example:
* Imperative: "Close the door." (This is a command)
* Question: "Did you close the door?" (This is a question)
Exceptions:
While rare, there are a few situations where an imperative sentence might end with a question mark:
* Rhetorical questions: These are questions asked for effect, not to receive an answer. For example, "Can't you see I'm busy?"
* Commands disguised as questions: This is a technique used to make a command sound less forceful. For example, "Would you mind closing the door?"
Overall, it's best to stick to the general rule: imperative sentences end with a period, while questions end with a question mark.