How does encryption help? Your client obviously needs to decrypt it so can't you just piggyback on that?
If you encrypt it, this is no longer possible. If a cheater wants to decrypt it, he has to get access to the decryption key, which usually is send over an TLS encrypted connection (with certificate pinning in place) [Or in some cases self made encryption :/].
Therefore he has to either reverse the game to get the certificate or has to attempt to read it while the game is running. In the first case the game developers (and the Anti-Cheat providers) will try there best by obfuscating the specific regions. And the 2nd case is basically what AC is all about, and therefore difficult for modern Anti-Cheats.
If they encrypt before the network functions, you can just look at the callstack and trace the variable containing the buffer backwards until it's non encrypted.
Sometimes you will be forced to hack the software, to allow interception or to replace a key. Unless they use a symmetric key that is easily found, but I have never seen that.
And then you have the monsters such as Widevine.
Versus just reading clean packages from a network.