From the technical side, PW code and data files are a mess. The more features PW had, the more mess there was. Some features are mutually exclusive, some are duplicated, some configurations of quests just don't work. Since we code the web editor ourselves, we do care about those things. Take quest AI trigger for instance. A quest can spawn or despawn monsters once started/completed/failed, and it does that by having trigger IDs coded within the quest structure. The trick is, the IDs are map specific. ID 10 on the FC map can spawn a boss, ID 10 on the main map can start the snowmen event. The quest doesn't specify which map's trigger to use, but uses the current player's map instead. It seems fair enough, but is fairly problematic to handle in the editor. - because we don't want to deal with any numeric IDs there, only specific triggers - but we don't know which one to use.
What's more, later PW versions wanted to spawn monsters via quest at any map (e.g as a result of using a consumable item - which works by just activating a quest that's immediately completed). They added a new, per-quest list of monsters to spawn. In the end, a quest could spawn monsters either by activating a trigger on the current map, or by specifying monsters in that list.
It's actually reasonable to add such list, but the previous trigger ID should be then removed, and all existing quests should be converted to use the list instead. That is extra, unnecessary work though, so it's no surprise it was not done. This left us with a burden of having multiple ways to achieve some functionality. Coding the editor for all those ways is extra work too. So that's an another reason we stick with the good old PW 1.3.6