Things like hardcoe mode are often left out because they are basically impossible to balance, and they better left to modders who can create systems with far more control over rates, like how fast you get hungry, rather then trying to force some hunger rate a player might not like as devs do when making hardcoe systems.
NV's vanilla hardcoe mode was absolute garbage, and most mods just replaced basically the whole thing anyways. Why bother spending time making something you know is just going to get replaced anyways?
Its one of the few things modders can do far better, since modders can offer far more control over the systems then devs can/are allowed to.