Phrases & clauses are needed because they add a lot more meaning, or, "flavor" to your sentence, and you need clauses especially because you need to have a complete sentence as well as a "flavorful" one.
English needs colons and semicolons to add emphasis and help express thoughts better (add "punch").
Dependent clauses depend on independent clauses because they can't function as stand-alone sentences and need independent clauses to make sentences.
Subordinating conjunctions are used to transition between and connect ideas, as well as help the reader understand which clause is the most important.
1. "Because your grades are bad, we're taking your phone away." 2. "I'm upset because I failed my test." 3. "Since I was sick, I stayed home from school." 4. "I needed to stay after school because I didn't know how to do my homework." 5. "Sice I had the money, I bought tickets to a baseball game."
Semicolons and colons are used to make lists, describe things, and link sentences (semicolons only) Ex: I had three things on my breakfast biscuit: Bacon, egg and cheese. A squirrel is on a tree in my backyard; my dog chased it up there.