Some disputes can only be handled by the mod who issued them. We don't keep any records on TWC's, so those are almost impossible to reverse except by memory. We also can't answer bans for evasion unless the mod who issued the ban posts the name of the account that the member was accused for evading on, or how they found it. Bans issued to hacked members can often only be answered by the mod who ordered it since it can be hard to trace how exactly the hacking came to their attention, and any scammed members must be paid back before the user can be unbanned, etc.
Then there's the problem of disputes that don't link to references. If a member gets banned for scamming and disputes it, for example, their story must be matched against the evidence. If their name is too short, contains unsearchable characters, or was reported by someone who forgot to say or mispelled their username, the original report can be difficult to locate. The responding mod has to go through the hassle of checking the ban date against all reports answered that day, with no guarantee of even finding it.
Not to mention, a number of those disputes are older than a month, and simply haven't been locked since "nope, sorry, more than a month" is probably a worse answer than none.
Why do some reports get answered before others? Often, it's quite simply because they can be.
I agree that there's a problem with a dispute forum, particularly with some mods not following-up on the infractions or bans they issue. But, it is a hard forum to regulate.