Well... in theory, say you work your ass off for two years to make a music album. But it only sells 1000 copies, not nearly enough to provide for the 2 years of labor + costs. And everybody keeps lending out or selling their copy of the album. Over a period of 3 years, maybe 10.000 people enjoyed your work, but only 1000 of them paid you. Doesn't matter "where" or "who" has the physical copy at one time. Had all of those 10.000 paid for the music they did listen to, that would make a huge difference financially for the artist. For a movie, this applies even more, because once you've seen it, you won't be doing that again soon (in most cases, or not more than a couple of times), where as music can be appreciated more after listening to it 10 times. I think games work the same way as movies.
Of course, game publishers are a business, and not in it for the love of gaming. I also think there has to be made a distinction between game devs that are looking for a publisher for their game, and publishers that own IP's and are looking for a dev for their game. I think in the latter case, the dev can work for how long they get paid, and they'll get paid anyway. In the former, they are much more vulnerable i believe. Hence so many devs closed down the past years. For every publisher that goes out of business, a multitude of devs has gone out before.
One could argue if the price point might be the problem. Maybe games being lots cheaper would easily sell double the amount and people wouldn't feel the urge to sell/buy used games because it wouldn't be worth it.
