Why don't more boxers TURTLE?

I've been boxing for a while (just training, sparring a little, etc). I've started taking Jeen Kune Do for the 4-5 months. All there **** is your lead hand/ lead leg infront. So, I fight my martial arts instructor (5th degree black belt), and I get DESTROYED!!! No kicking, but he's aloud to backhand. So, I started getting deeper and deeper in to this training...Lead hand infront. I could fight both before, but now in southpaw I'm very fast, and deadly against most people (plus they aren't use to fighting soutpaw fighters).
So, I beat quite a few people using this method, and it works really well...The people it doesn't work against are....people whom know Jeen Kune do BETTER than you! Which are my instructor, and a student he trained for like 4 years.
It was like 4-5 months since I got destroyed so I was plotting a way to beat my instructor the whole time. He's a counter puncher...He puts his right leg out infront a good distance, with a spring (for mule kicking people coming towards him), leans his head back making himself impossible to hit for even stretch armstrong...SO, you must come to him, and he'll counter you (usually with a backfist), and then beat your ass. His student will do the same. So, I figured my first plan was to ATTACK! Kind of like a Manny Pac charge. Worked alright against his student, and I was proud. Tryed it against the instructor...TORE ME UP HARD!
So, I put a new plan to action...TURTLING. I still come at them, but turn my gloves in to me making it very hard to hit, tuck in my body, and fight CONVENTIONAL. Since he's fighting southpaw I'd block most of the right hands with the left glove, and counter usually with the left hand. Worked like a damn charm.
My question...Why don't you see more boxers do this style that are counter punchers, or even guys whom are looking to get in far enough to work the body??? Also, if I use this style, what are it's disadvantages....What do I have to watch out for? He'd slip the occasional uppercut through my defense every once in a while, but couldn't do much else otherwise.