Here's why:
* Subordinating conjunctions connect a dependent clause to an independent clause.
* Dependent clauses cannot stand alone as a complete sentence, while independent clauses can.
Example:
* I studied hard in order that I could pass the exam.
In this sentence:
* "I studied hard" is the independent clause.
* "in order that I could pass the exam" is the dependent clause.
The subordinating conjunction "in order that" connects these two clauses and shows the purpose of the action in the independent clause (studying hard).