I agree with your initial thought, but instantly banning the account that was using hacks would be too unreliable of an approach. There's so many things that could have happened which could relieve the player of their ban. The person's account could have been unknowingly accessed, the person could have had a sibling play without their permission, or the person could have not been hacking at all in the first place and was falsely banned. So yes, while hackers who intentionally hack to ruin others' fun should not have a second chance, it's almost impossible to differentiate those hackers from the less severe cases that I mentioned before.
Think of it this way; you enjoy playing on Mcsg, so much in fact that you bought a shiny new Diamond Donor upgrade for your account. A few weeks goes by and you notice that you're banned on the server. You look at the evidence and have no recollection of playing in that game, and come to find out that someone accessed your account and used an illegal client to have you banned. Now there's absolutely no chance of you ever playing on Mcsg again, because no one would believe that someone hacked your account without proper evidence, and now you've wasted $75 that won't be refunded to you.
Or what if you're an extremely skilled player, and you try your best to win in every match you play. You come across an equally skilled player and manage to defeat them, but they assume you're hacking and go on TeamSpeak to get a staff member's attention. You go on for the rest of the match but are kicked and banned halfway through. You try to dispute it but the evidence is accepted as true and your plea is declined. Once again, you're completely disallowed access to the Mcsg network without another chance.
Long story short: Instant perma-bans are flawed, and don't leave enough room for false bans to be corrected
