Equipment... Don't need, can buy it. In fact I'll just end up leaving it behind because of carry weights and vendor limits anyway.
Materials... Again, can just buy them and the more you stock the harder it is to have inventory space for more stuff.
This makes little sense to me, if you go out and explore and adventure, you will get better equipment. in fact, most equipment you found on your adventures are better than the stuff you can buy. The same goes for material.
Quests... Whose rewards are? Nothing because you cannot get any profit from the loot as the merchants are already spent from the main storyline.
The rewards are more interesting world information, unique items, money, experience.
Experience... Yes, I'll give you a point here if you do are feeling the difficulty and need a level or two to get back on track but I doubt it is really needed.
But you haven't gotten past the drill part, levels and skill increase is very much needed throughout the game.
Interesting storylines... Again you do have a point here, but if I get nothing from it, even if I did it only once to know them, that's all there would be to it, no replay value with them as you already did it once and from there, given that there is no reward for doing it you won't need to do it again ever. Much like the GMS vault. You go there once, get nothing worth your trouble, speditures and time and you don't touch it again. Waste of time for both players and developers.
That's depending on how you go about it, some of the stuff you do branch and can only be experience one way per playthrough.
It is not all about the loot, but it's mostly about the loot. It's an RPG and as such it revolves around loot a lot. People play games because they enjoy playing games. Everytime they beat something tough or get rewarded for their work they get a dopamine release which gives them the pleasure. In these games the loot is what gives us the enjoyment, it's our reward, our dopamine release. Basicly the game is denying you that.
That is actually not true. There are sub-genres of RPG that centre its gameplay around loot, most notably action RPGs. Traditional CRPGs* are less common to revolve around the stuff you get, it's mostly about world building, unraveling storylines and most importantly player choice in relation to the story and the world at large. Some RPG games have very little emphasis on loot such as The Witcher, Mass Effect, Planescape Torment amongst others. There are many different ways to make RPGs but that's a whole other discussion not really related to the topic at hand. Just wanted to clear things up a bit.
*With Traditional CRPGs I mean RPGs like Baldurs Gate, Fallout, Arcanum, Planescape Torment etc.