Why do I get matched with so many diversely ranked players

Gold 3 trashcan here, I am just wondering why I get matched with people outside my rank. If nearly 30% of players are gold why do I often see high silver and low plat players in my games when I'm mid gold. I know OP.gg isn't perfect but I think their mmr scale is pretty close to accurate and often these silver players have silver mmr. It just seems weird how I can play with players from another division when my division is so huge, I would rather have to wait 30 more seconds in queue to get 9 other gold players.

Anybody know why this is?