In short, because D&D is poorly suited for video games, it's actually possibly the worst tactical combat system used in video games ever. Why?
- you have to rest between spell casts (wtf) - you have to prepare spells (why???) - you are extremely limited in what one character can do in one round (too slow and boring) - health pools and damage numbers are too low which takes away fine grain progression from the game, and they're low because the entire system is designed for a physical dice - in general combat is very slow and clunky
Yep, thats because its not *just* a tactical system, it's also a logistical system. It's a few layered systems really, but I won't get into all those.
It's important to understand that D&D provides a lot of different ways to play it - all those systems you mentioned are one dimensional - which is fine but also limiting.
Some people like to play D&D adventurers like a survival horror or escape horror, with slight modifications.
