Dude, this thing also happen sometimes in 4k matches. The problem is that players have such a tunnel vision playstyle that their map awareness is complete shit. So buying wards is a non factor that contribute to their downfall. The main difference between a good 4-5k players and a 2-3k players is the rotation. Most shitty players will just stay at their lane without going to help your ally where else a good player will always rotate. This my friend is the main diffrnce.