Part of games (the engine) is software. People can benefit from this
software. This isn't just theoretical: just look at many of the free
first-person shooters out there. Many of them use free engines that were
available, such as the Quake engine (OpenArena, Xonotic) or the Cube engine
(AssaultCube). Heck, there's even one based on the Doom engine (Freedoom).
Then you have the question of longevity. If a nonfree game falls out of
support, there's nothing you can do about it; you have to just hope that the
future systems you're going to use will continue to support it, or keep an
outdated system just to play the game.
But that's just the shallow open-source argument. We need to remember the
most important reason game engines need to be free: they are computer
programs. If they are not free, we do not control our computing.
We can't make an exception to games just based on who the primary users are,
and how likely they are to take advantage of these freedoms. Most people are
not likely to take advantage of any freedom in their computing at all. That
does not make it right for them to not have freedom.
In addition, like all nonfree software, nonfree games often contain malicious
features, such as surveillance features, backdoors, and the nonfree game
industry's favorite: DRM. Our only defense against such features is to use
only free software, including game engines.
