Valve uses a hidden system called "Trust Factor" to match players. If you constantly get matched with toxic players, griefers, or fresh accounts, your Trust Factor is likely in the gutter.
What Lowers Trust Factor?
Abandoning Matches: Leaving a competitive game before it finishes is the fastest way to destroy your score.
Team Damage & Griefing: Consistently getting reported by your teammates for anti-competitive behavior.
Account Switching: Frequently logging in and out of multiple "smurf" accounts on the same PC flags you as a volatile user.