I think a problem with danger zones is that 5e's rest mechanics are ill suited to a videogame. If a player enters a danger zone, uses a short rest after the first two encounters, then in the third uses up the rest of their resources and after that they have a boss encounter they could enter that encounter drained of resources and unable to continue. Then what? A DM could fail forward something like that, but on a computer the best case scenario is they reload a save from three to four hours earlier and start over. That would just suck, for a lot of people thats uninstall and write a negative review territory.
If Danger zones are limited then they could always be placed in scenarios where fail forwarding is accepted, but in general for a long form game its not good for failure to be seeded hours and hours in advance with the player unable to see they've already lost.
Or people could just lower the difficulty...
Conquering Drezen in WotR felt so much more satisfying by managing to pull through on the skin of your teeth because resting was limited instead of you just hitting rest before every encounter.
