They only do this if you train them to. My dog knows that there is no way in hell that I’m ever going to give him table scraps, so he leaves me alone when I eat. My dad, on the other hand, always gives him little bites of whatever he’s eating, so the dog never leaves him alone when he eats.
P.S. I hate to sound so unfeeling but I have some pretty strong feelings about the negative aspects of our dog (and her main owner, who undermines mine and my mother’s authority over the dog with his weakness for the dog’s desires, i.e. food)
Or try a Halti, which is a little different than a “Gentle Leader” type deal. Not sure how they differ, but my dog’s trainer recommended that.
Cured my puppy of pulling, it did. And it keeps the nasty kids on my block from wanting to pet her all the time cuz they think it’s a muzzle. heh
Make sure you read the directions that come from a Halti. In my experience, you have to strap it on the pooch and drag them around in circles for a while before they get the hang of it. Dogs don’t really like stuff strapped on their nose, but they do learn to “respect” the Halti. And since their jaws and noses are so strong, it doesn’t hurt them.
Blush 
Heh… I am a professional dog-walker, and picking up poo with a plastic bag and being dragged everywhere is my job! 
I pit thee, dog who pulls me around with single-minded sniffing intent, and only looks at me when I toss you a cookie. I pit thee also, dog owner who never felt the need to train your dogs to walk nicely on a leash when they were pups – small and manageable – and now looks to me to teach manners to the two-ton *oxen * you call “labs”.
I pit thee, dog who poops three times when I only have two bags, forcing me to re-open one foul bag. I pit thee also, dog owner who feeds the dog human foods of wide variety, ranging from apples to blueberry muffins to steak, so that your animals suffers from near-constant diarrhea, which is not easy to pick up, gets everywhere despite my best efforts, and smells horrid.
I pit thee, dog who seeks out the poo of other dogs and eats it.
I pit thee, troubled and angry dog who refuses to let his feet be touched. There would be much less trauma if you’d just let me remove the burr from your paw. It could have been your foot, my hand, and no pain. There was no need to involve a second party, a bath towel, wrestling manuvers, or your teeth. I suppose you’re lucky that the antiseptic and bandages were just for me.