I agree that it is because the eggs are fresher. Old eggs which is the norm for many eggs from the store peel easily.
Another tip in addition to the vinegar, or letting them cool or dry out before peeling, is to boil with potatoes in the water. Never tried it but I am told that it helps too.
Or you could just age your eggs a little if you need that easy-to-peel surface. I'd rather have them fresh and work with it myself. Start at the wide end, that may help a bit too.
If you want to tell how old your eggs are before you boil them, you can submerge them in cold water and see if they point upward at all. Fresh eggs will sit horizontal on the bottom, older eggs will start to point upward. If they actually float they should be thrown out.
