I know that in MLA format a parenthetical citation has to come right after the quote and before the period, but WHY?

I'm not sure why!

I've always figured it is because the citation is needed with the quotation and therefore both are part of the same sentence. The period comes AT the end of the sentence.

What is the simple subject and the simple predicate of the following statement: Where did you get that ice cream?

The reason a parenthetical citation in MLA format is placed immediately after a quote and before the period is to attribute the source of the information or idea to its original author. This allows readers to easily locate the full details of the source in the works cited page. Placing the citation immediately after the quote ensures clear and accurate documentation of the borrowed information.

To include a parenthetical citation in your writing, follow these steps:
1. After a direct quote or paraphrase, place a closing quotation mark or end the paraphrase.
2. Immediately after the quote or paraphrase, insert an open parenthesis.
3. Inside the parenthesis, include the author's last name (or the source title if no author is provided) and the page number(s) where the information can be found.
4. Close the parenthesis.
5. If you include the author's name in the main text of the sentence, you only need to include the page number(s) in the parenthesis.
6. If you do not mention the author's name in the sentence, include the author's last name (or source title) and the page number(s) together in the parenthesis.
7. Place the period after the parenthesis to signify the end of the sentence.

Remember, the specific guidelines for parenthetical citations may vary depending on the source type (book, website, journal article, etc.). It's important to consult the MLA handbook or a reliable online resource for accurate and up-to-date formatting rules.