Originally Posted by
Cracked
The argument of scarcity is the real difference. You tried to preempt it, but truth is, you can't make it the same. Or if you want, you can argue that by buying a concert ticket in advance, the product is that they agree to not sell your spot to anyone else. Same in plane tickets. Limited seating, first come, first serve. Plus they usually make it worth your while to "prebuy" with cheaper price.
But in online distribution, there is no such factor. Companies try to sucker you in to basically "lock it in on hype", by attaching mtx to preorders that won't be obtainable later, essentially fabricating false scarcity. The point is, you don't preorder unless you have to. The price is not any cheaper, and don't worry, they aren't going to run out making digital copies of Shadowlands. As a consumer, it basically gives you the leverage of opting out of the sale at any point until the product is actually deliverable.
Edit: As to "preordering groceries", there is a component of trust because they probably work on repeat business. Does them no good to fuck you over today if that means you won't use them tomorrow. With corporate structure, these companies (or at least management) really only care about a box sale. Once that is done, they don't expect repeat business for years at minimum. It's a psychological thing.