For certain publishers this may be true, but as an avid game collector and someone who also has a collection of 700+ games on Steam, the complete opposite is true most of the time. The only game company that consistently keeps their physical games at top dollar for a long time after release is Nintendo, and you cannot purchase their games on PC anyways. For other big names like EA, Activision, and Ubisoft, and others, their physical copies typically drop in price much faster than their digital versions. I was able to purchase both the new South Park and Assassin's Creed Origins on PS4 just a little over a month after release for $15 each, brand new. There was no way you would even hit close to that price on any digital market. Many niche PS4 , Vita, and 3DS physical games get clearanced at a fraction of the cost of their digital counter-parts that rarely go on sale. A good number of physical copies drop in price 2-3 months after release so that stores can clear shelf space for newer games.
On average, I would say that physical sales and clearance occurs far more often than digital sales, especially if you know the ins an outs of retail clearance schedules. It goes both ways of course, but if I have to track down a game at the best price available, I am willing to bet I can find the game at a better price physically in the same time frame for a majority of the time. This is in the U.S. anyways and won't apply everywhere.
The only console game company who has a unified approach to gaming is Microsoft, where they are making many previous game purchases from the Xbox / 360 available on the Xbox One. However, this is an extremely slow process and occurs on a game by game basis. Nintendo also does it for certain games where you can repurchase content at a discount from Wii to Wii U, but nothing applies for the Switch yet. As others have already stated, people have lost previous online purchases through closures of the DSi store and soon the Wii store. Another digital service that closed their doors and online purchases were lost is OnLive. While this was a streaming service, it still goes to show that your purchased access to these digital games can disappear without notice if a company unexpected shuts their doors.
While mega companies like Steam, Microsoft, Sony, and Nintendo won't likely be shutting their doors anytime soon, I would be willing to put money down that some of their current store fronts on older consoles will be closing their doors over the coming years. Sony already shut down their PSP storefront a couple of years ago. Games are still accessible through their online PC store, but for how much longer will that occur? Sony has a history of re-releasing games from one console to the next without any ability to transfer purchased games from one generation of system to the next. I would not be surprised to see Sony shut their PS3 store down in the next several years, especially if they release a PS5 in the future.
In reality, the digital store front for older consoles have their days numbered. There is no way you can tell me that you believe that you will still be able to connect your PS3 onto the internet 20 years from now and still redownload your purchased games. There is just no way Sony, Nintendo, and other companies will host these games forever.
