Game preservation seems like such an odd thing to care about.
Keeping media around in order to understand history better, for game design purposes, for the sake of knowledge alone, is a worthy cause.
Just talk to any fan of oldschool films. Apparently, of the thousands of early silent films released by major studios, about 75% are completely lost, and another 11% only exist with compromised quality. That means maybe 1 film in 7 from that era is left intact for future generations to enjoy. And from the early era of sound films from the mid-20's to 1950, about half of theatrical films released in the USA are lost.
In the world of music, we have no records of Mozrt's Cello Concerto in F or Trumpt Conerto, Beethoven's original version of Ode to Joy, and various pieces by Bach.
And according to the Lost Media wiki, there are over 670 Lost video games. Sure, a lot of these are unreleased prototypes or whatever. But a lot of lost or seemingly lost games were fairly complete projects of some quality, or at least are important for historical reasons (Legend of Zelda on Satellaview, Radical Dreamers, Resident Evil for the Game Boy Color, Sonic X-treme, various early mobile games, etc).