See, here inlies the problem. So many track promoters are turning to a treaded tire rule thinking they will be saving the racer tons of money. It couldn't be farther from the truth. Treaded tires cost considerably more than slicks, come in difficult sizes to stagger, and are way over-kill for tread grip for an underpowered kart.
Because they virtually lock the kart down, it creates follow the leader racing, especially with spec engine classes.
So, the racer looks for an advantage. First in sizing, then in cutting some of that unwanted tread off, then to prepping. By the time you're done with a set of tires, it costs $100 more than a set of dirt slicks.
You're going to need to read through the other thread as well, but consider that while slicks are faster than treads "nearly" always, there are some tracks and conditions that make running slicks difficult at best when running against guys on treads. The treaded tires tear up the track by throwing rooster tails of dirt up in the air behind the karts running them. That dirt falls back down into the racing line and makes a bed of marbles for the other racers to run on. Obviously, some track surfaces won't be affected as badly as others. Many here in the midwest and southern plains states end up like a field of marbles, and everyone has to bolt on treads, or slicks with grooves cut in them just to get ahold of the track.