Depends on the system. If you want to see it done really well, look at Stardock. You buy a game from them, you are really just buying the activiation code (your license). You buy from a store or a retailer and you can still go to their online site, put in your license, and download that product from them, years later. It’s all the same to them. You pre-order a game from them, you can download it and activate it at midnight on its release date. And they’ll still send you a copy of the game, if that is what you ordered.
The trick is that once you are doing digital distrubution, you (usually) have the infrastructure you can then leverage to provide whatever other mechanisms you need to manage, and allow the customers to manage, their licenses. It makes for an excellent copy protection— as each game needs an activiation code. If you worry about piracy, you require one time online activation— which no digital purchaser can argue with. They had to be online to get their product— and for the PeaPri customer base, you let them deactivate a code so they can then “sell” their license to others.
With that sort of system in place, there is no reason not to allow people that pre-order a game to download at release. Send them their code in email, let them hit the servers. In fact, as pre-orders, you might let them hit the servers early (up to a week or so), and so all they have to do is start their product at midnight, and activate it. Some people would still pre-order the game with a physical (hard) copy. The amount would go down for the hard copy, but pre-order amounts would stay stable overall.
It’s up to Peach Princess. They are doing the digital sales right now so they can take advantage of the “long tail” on their older products, while minimizing the overhead cost associated with their older products (no need to order 1000 units printed, as they have a very cheap “print on demand” due to digital copying— no need to for those older units to be taking up space in a warehouse, as they can just take a bit of space on a server instead, etc etc etc). PeaPri is just currently fighting against the pull to go further in that direction. They want us to pre-order hard copy games— even though they aren’t large suppliers (or at least, don’t seem to be) of such to their “retailers”. Having a physical presence does help spread the games (and therefore grow the business), but I wonder if it is worth the aggravation to its more far flung customers? Won’t online ads do as much to grow their customer base as having the games on hand for a few merchants to take to anime/SF/gaming conventions and having a few other merchants online offer their products? Do they need physical copies so that Amazon can sell them? I don’t know— maybe they do. Maybe those physical copies, being sold through those other sources, help them grow their customer base. I certainly hope so, but I haven’t even a wild guess about where their new customers come from. I found them through the internet almost two decades ago.