Here's why:
* Compound sentences are made up of two or more independent clauses joined by a coordinating conjunction (like "and," "but," "or," "so," etc.) or a semicolon.
* Independent clauses are complete sentences that can stand alone.
* Dependent clauses cannot stand alone and need an independent clause to be grammatically correct. They often begin with subordinating conjunctions (like "because," "although," "since," etc.).
Since compound sentences are made up of only independent clauses, they don't contain any dependent clauses.