I hated it at first because everything was so new, but I think once we get used to the quick access slot, buying items should be a lot faster.
(I know, such an analogy, but why not)
Imagine a cyber cutlet from CS:GO who loves AK-74 weapon with its wrong recoil and firing, and here, valve comes such, fixes this recoil and firing, what do we see? That's right! Cyber cutlet will hate the developers and demand to return everything as it was. (This is by the way the first reason why CS:GO has not changed for 7 years)
Here too, 3 years using the same layout with the purchase of the store and do not want to get used new layout, because it is not convenient. Also, how this tab moves down all the tabs, especially "Tools". It is very painful.
And unfortunately many people don't want to retrain for something new. (I hope it is not necessary to draw an analogy with system administrators)