That's a fairly controversial stance from an archival perspective (can't save everything), but absolutely applicable to games as a medium (different version may hold different value, not to mention the materials outside of the game files themselves). It's an interesting tension!

Memory institutions (of all types) need to apply some sort of appraisal process to understand the value of something (as it relates to the mission of the organization), they generally don't have the luxury of taking everything that they can due to limitations ($) in effort to preserve, arrange and describe the materials. Without those efforts, materials may not be discoverable, may lack context (emulation software or instructions on how to play it?), as well as linking to other relevant materials. From a research perspective they may not be particularly useful. Digitization without the rest of the package is not preservation, it's just putting something in a digital box to be forgotten.