Because nobody likes playing with cheaters.
Playing games should be fun. In order to ensure the best possible online multiplayer experience, Valve developed a state-of-the-art anti-cheat system that automatically detects and permanently bans any player using cheats or hacks on a VAC secured server. What this means to you as a player is that you don't have to worry about annoying cheaters getting an unfair advantage and disrupting your game.
The Valve Anti-Cheat system is only enabled on servers with the secured shield logo and only Valve has the ability to VAC ban a user. While server admins may choose to ban players from playing on their specific servers, they do not have the ability to VAC ban players. The VAC system is automated and contacting Steam Support to report cheaters isn't necessary. Valve has a zero-tolerance policy for cheating and will not lift VAC bans under any circumstances.

♥♥♥♥ IT we`re just gonna get a beatbox here ight check it out checkit out lil music uh for the stream uh for everybody that doesnt have music lego ight so check it out BOOTSH BOOTSH BOOTSH BOOTSH BOOTSH BOOTSH BCHE CHECK IT OUT YO BCHE UH BCHE UH BOOTSH BOOTSH CHECK UH BOOTSH YO B

BUH BUH BUH BUH BOOOOOOO check it out yo buh eh buh uh ubebubububu EBBE

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