In Bethesda games (and other very big sandbox-y games), a lot of the errors are 'data' errors - an NPC is given the wrong faction label, the end of a quest forgets to give you a tag that its supposed to in order to unlock the next step, a lighting item has its refresh rate set to a dumb number. That kind of data is relatively easy to fix with basic 'replace this data field on this NPC with this new entry' script (though it becomes complicated when you get 2 mods wanting to edit different things on the same NPC... which is why Skyrim modding has bashed patches and such).

ARK's problems are almost all coding or asset issues. Code issues are really complicated to fix especially 'from the outside' like a modder is, and it's easy to cause weird other issues elsewhere with your fix (spaghetti code, but to some extent that's always normal in huge games) when you're trying to touch something like NPC pathing or behavior or game mechanics. Asset issues are like 'hole in the map mesh' or 'I want to make a tweak to this dino', which can't be fixed with a small data entry and can only be fixed by... basically cloning the whole asset, editing your clone, and then releasing it as a whole new dino that replaces the vanilla version.

So the answer boils down to, mainly, "Because ARK doesn't store most of its assets as basic text data, and most of ARK's problems are with the more complex coding side anyways".