Actually, that is Exactly why you should educate yourself on it, especially if you are going to pass judgment on it. How can you have an opinion on something you know nothing about?
it is like: "I hate broccoli." "Have you ever tried it?" "No" "Then how do you know you don't like it."
You really can't say "The gi is only useful for gi competitions" when you have NO idea what you are talking about.
Sure many BJJ academies are directed at sport competition. However, you seem to be unaware that there are GJJ academies that focus purely on self defense, and do incorporate strikes. Also, contrary to your opinion, you can choke someone out with the cheapest, thinnest T-shirt ever made, without tearing it. You just need to know HOW. Lastly, muggers will typically wear clothes. I think even rapists will be wearing some sort of clothing. Grabbing clothes is FAR more realistic than not grabbing clothes in a self-defense situation.
The old saying "You don't know what you don't know" proves true. Don't make statements you know nothing about is all I am saying.
Peace.