Having not really done any endurance events I’m probably not qualified to comment however I can see slightly more appeal in an “unsupported” point to point 24Hr racing than a lapping format in terms of it being more of an "extreme" challenge, you’d have to plan for a full 24hrs not X number of laps at a time, like you say water, food, batteries and the pretty massive amount of logistics and organisation required once you go from marshalling relatively short laps to covering silly distances is always going to be the sticking point…
Totally unsupported racing i.e. you can’t even scrounge water from sources along the route you’d need to carry ~53Lbs of water (assuming 1Ltr/Hr) then you need food, spare batteries for lights, tools, tubes/patches, possibly additional layers depending on conditions anyone lining up at the start without around 70Lbs of kit plus their bike will probably need rescuing before the end of 24hrs, panniers FTW I reckon…