Because they're for staff, not players. Staff have discretion of how they handle situations, the guidelines are just a baseline for the punishments. A good example would someone saying extremely offensive things/trolling hard and being banned with one warning and then appealing saying that the guidelines say he should've gotten 3 warnings or trolls complaining in global every day that staff "abused their powers" and not acted within the guidelines. Things are still better with some discretion, as situations should be evaluated on a case by case basis, not a black-and-white basis.
Who are you to say that that knowledge is for staff only? IRL, laws are public. Not everybody is compelled to know the law (that's why we have lawyers), but everybody has the right to study and learn it, if they want. Why should I be deprived of the right to know that, say, "scammers are punished with ban and if they successfully appeal they will face a 3-days tempban (5-days or more if repeated offender)"? (I made this out just for the sake of making an example) Their appeal would be dismissed because the unban counter-reason doesn't show any remorse, and the mod who banned him would be (internally!) reminded to warn thrice next time (or else, this would be a case in point showing that the rules should be changed to "only one warning might be sufficient in extremely serious situations"). Rules are rules and they need to be clear and public, in order for them to be respected by everyone (players and staff).
Just to clarify: it has been said that, if punishments were public, offenders might find loopoles. Well, if there really is a loophole, then upon its discovery the loophole should be promptly solved. And if there isn't, then... what are we talking about? But let me add one more thing. Punishments should be public not for the sake of those who face the punishment: punishment should be public for the sake of those that might be victim of someone else. If I do business with someone, and I take some risks, I want to know what the counterpart will face if they try to scam me. It is my right, not their, to know the punishment expected for scammers. Only in this way I'll have something to take in account when evaluating the risk to do business with them. In other words, public rules are required to build trust among people who want to self-preserve.
ECC isn't a court of law though - It's a privately owned entity. All regular players need to know is the rules which staff act by, and stay within the rules, and you should be fine. When you give people public access to the guidelines staff are supposed to act by, people will start to abuse them in many different ways like finding loopholes or trolling mods like trying to get exactly enough warnings before the mods are permitted to ban them as per the guidelines, or in my last example, complaining they "didn't get enough warnings" when they appeal even though they were trolling hard. When you have guidelines that are literally interpreted as the only way staff are supposed to deal with situations, you begin to have a problem - as I've said in my last post, You get banned for scamming, that's the punishment that a person always gets for actions of that sort.
@kukelekuuk00 Would the guidelines as a whole be vague, or just the guidelines publicly available to players?
Well, I'd actually support something like that. The full guidelines should remain private regardless.