Here's why:
* Simple sentences have one independent clause. An independent clause has a subject and a verb and can stand alone as a complete thought.
* "Asking a question" does not have a verb. It's a phrase describing an action, not an action itself.
To make it a simple sentence, you would need to add a verb:
* "I am asking a question."
* "They asked a question."
* "Does asking a question make you feel uncomfortable?"
These are all simple sentences because they have a subject and a verb.