Exactly, couldn't have put it better myself.
Full quad rail makes the front end of the gun significantly heavier (it may be pretty difficult to believe, but adding 150g of extra weight on the front end of the gun just makes it so much more difficult to maneuver!). Furthermore, quad rails can cut hands open easily, unless you wear gloves (they also cut up gloves pretty good, if you are doing a lot of shoot - reload- shoot drills on a daily basis, you are gonna need to switch gloves very often when your gun has quad rails). Most countries are not longer going for the quad rails in their new rifle designs, more modular and lighters systems are preferred. After all, mlok or keymod like systems are lighter, more ergonomic, cheaper to make, and more versatile than quad rails.