The "realism" regarding the extreme rate of beneficial mutation from radiation doesn't bother anyone in Fallout but the lack of an inventory weight limit does... I just don't get people...
FWIW, you're right, and I don't just mean in the opinion sort of way. People with issues about this kind of thing just feel more comfortable with the tropes they're used to and I curse AD&D for ever creating this one (it probably had prior art as well, I'm just not aware of where they might have stolen their encumbrance rules from).
Encumbrance in AD&D makes sense to some degree.
I like encumbrance that is applied to armor and weapons, because it adds another dimension to the strength stat (beyond simple to hit and damage bonuses), but that's mostly because weapons and armors are such vital and physical pieces of gear (not to mention apparent).
For weight restriction on other gear, I think it was mostly to prevent abuse and enforce game balance, especially in pen and paper games.
For example, in one of my game, a novice player who was very strong was murdering guards in their beds and then wanted to cover his tracks so he tried to leave with all the guards he murdered and their mattresses...
Similarly, a filthy rich player could be overpowered if he is allowed to carry like 100000 gcs on his person all the time, but if you introduce logistic problems to carrying so much cash on his person, then you balance the game somewhat.
And of course, there is the well established wealthy mage that could carry an arsenal of potions and wands (3rd edition balanced it somewhat by requiring an XP cost to manufacture those items... in the 2nd edition, all you needed was money, time and ingredients and sometimes, years could pass in game time between campaigns...).
A computer RPG is much more restrictive in how abusable things get (you might find a RL way to abuse an absurd mechanic, but if it wasn't programmed into the game, you won't be able to) and furthermore, it is a lot more constrained in how realistic it can be so inventory management makes a lot less sense there.
I think they should mostly skip it (except maybe for the armor & shield the character is wearing plus whatever weapon he has readied), except perhaps in very extreme cases if it really caused a problem.
If you really want to use inventory management as a way to force the player to make a difficult decision with his gear, then make most of the missions in the game more time critical (put some sort of deadline), make towns very hard to access or create a more realistic economy ("sorry pal, can't buy that full plate from you until I sell some stuff, I'm out of cash and credit doesn't exist yet") so that the player doesn't can't just go back and forth between towns and the mission with impunity (because if they can, they will, but they won't find it enjoyable... I think most people just can't help themselves).