It is not really a black and white thing like that.
For example, on Steam you can buy games from their marketplace, but you can also buy them from 3rd parties at varying prices (including Amazon/Ebay/BestBuy/etc.) and then just input the code to have the game added to your library. It has been a pretty common practice for the last decade, even on digital games from PSN and XBox Marketplace.
Half of my Steam library was not even bought on Steam.
Apples vs. Oranges.
It totally is a black and white thing. Think of Sony unexpectedly discontinuing PSMobile and making the (purchased, from PSN) PSM libraries useless. They offered a limited time code to "activate" PSM games, but they can't be transferred, backed up, etc, and any purchased game you bought that you didn't "activate" within the time limit is useless.
Steam: how many console games are available through Steam? Consoles have proprietary BIOS and only play games for that console with DRM, while computers from different manufacturers will play DOS, Windoze, etc. computer games.
I have 3DS games bought through Humble Bundle, but the code is still for the Nintendo Store, not an independent vendor.I
Imagine a digital future with (for example) SCEA unilaterally deciding what games you can play, for how much, and deactivating games you have bought when THEY decide they are obsolete or no longer profitable to maintain a storefront for.
That has less to do with digital specifically and more to do with consoles in general.
It is understood when you buy a console you are tied to games specifically made for those consoles, just like it is understood when you buy a game for Steam that it only works in Steam (although there are plenty of games you can buy on Steam where that is not the case). The same thing occurs if we have physical or digital games, that wouldn't change anything. Ever hear of the Nintendo Seal of Quality? It is the same thing as PSN or XBL.
Plus games leave a marketplace all the time, that is just the nature of game licencing. However, there has NEVER been a case of a game leaving your library other then something that is against the TOS. When you buy a game, it is yours. Saying that somehow it won't be is just unfounded speculation. Even when Nintendo discontinued the wii shop all the games that someone bought on there were still available and worked fine. If you show me a case where it has happened then I stand corrected, otherwise the conspiracy theories have no basis in reality. ---
I am a senior software engineer. If you see me post here, I am tired of writing TPS reports.