Chivalry is PC, so despite some extremely childish players ingame, odds are 90% of everyone is at least 20.
This is a forum, most people younger then 14-17 will basically use a computer just for schoolwork, and looking up cheats for whatever games they play, PC or console, not really being aware of the larger community at hand due to generally lower social awareness (Aka, less, there are people out there thing.)
Cutting out a large portion of the under then 18 crowd.
18 year old have just been freshly tossed out into the world of “I NEED MONEY! OMAWHGAWD” and likely cant afford anything fancy enough for chivalry.
Reasserting the fact that we are not going to see anything younger then 20.
Most people over 40 shy away from video games, or are tech repelled (Whether due to lack of tech savvyness, or due to hating tech (Namely, computers) at work,) enough that they would use something simpler then a PC…. Like a console!
So, really, this game is basically going to end up in this range regardless, due to it appealing to an ~arguably~ mature PC croud.