I would have paid 60 euros for Skyrim back in 2011. These days, I wouldn't spend more than 10-15 bucks on it if it was new. This is reflected in the price on steam as well, with it currently being sold for 15 euros.
The mere passing of time decreases the value of the goods, just like using a game would.
I don't know what happened that people think that selling things you don't need anymore second hand is suddenly bad just because the goods are on a computer. The car industry would love a method to stop people from buying second hand cars but consumers would never accept such limitations.
Games sales aren't affected by anything past the opening quarter. A study done by the EU on piracy concluded that even piracy is barely affecting the price of games after the opening period. Reselling games will barely touch the games industry.
Adding arbitrary rules just because the game industry is unhealthy isn't a solution to the problem. If I have to give up rights so that people can make some shiny toys every now and then, I don't care about those toys anymore. I don't want to give up rights to keep game developers employed because their current ecosystem is unviable. And, in my opinion, neither should you.