Like grammar nerds like to say, punctuation is a matter of life and death.
There's a huge difference between "Let's eat, Grandma" and "Let's eat Grandma."
Yes, grammarians can also be cornballs. But grammar truly is a matter of life and death… of your dignity as a writer. And as a human being.
In some canonized examples (Buzzfeed is part of the canon now, right?) a slip-up in punctuation could have you enthusiastically writing that,
"Man bacon makes everything taste better." Oof.
You could write that, "Rachel Ray finds inspiration in cooking her family and her dog." Oof. Oof.
You could post a sign in the disabled/family restroom at your establishment that reads "Attention: toilet only for disabled elderly pregnant children." Oof. Oof. And also—what?!
And it ain't just commas that spell the difference between cannibalism and family dining or embarrassment and writing proficiency.
Without periods, you could end up writing "I have two hours to kill someone come hang out." (Terrifying.)
Overindulgence in quotation marks could have you saying that your restaurant serves the best "chicken" in town, leading hungry would-be patrons to think "Uh, what is that chicken really made out of?"
Basically, all punctuation is there for a reason. It shows degrees of separation and emphasis. In fact, when you think about it, punctuation symbols are a lot like road signs. No, they're not huge and green. They tell your reader when to look alive and anticipate, when to slow down, and when to come to a complete stop.
Simply put, punctuation symbols are a powerful tool. Use them to get your audience to read your writing exactly how you want it to be read.
Feel the power!
Punctuation is, uh, kind of made up.
See, it was originally used to help people know when to pause in a sentence. Comma was a short pause, semi-colon was a longer pause, and period was a full stop. So who are we to tell you that YOU CANNOT USE A COMMA THERE?
Plus, with the thousand ways we now have to communicate, punctuation is always changing. Remember when a period didn't mean you were angry?
Those were the days.
Bottom line: take everything everyone says about punctuation with a grain of salt. Yes, you need to pass your grammar exam, but you don't need to deal with grammar tyrants.