There are many companies on todays video game market that knows it is both possible and quite prudent to stay behind the technology curve.
Case in point: Blizzard. Love them or hate them, they are arguably one of the most successful game developers this day.
With the exception of the first Diablo the technology they use have all been tried and true, perhaps even dated stuff.
Starcraft stayed with old-fashioned sprites while the rest of the biz were racing headlong into the graphics card assisted 3d-age. Warcraft 3 and World of Warcraft both chose a deliberate "cartoonish" style in order to reduce polygon usage and reduce the demand for advanced lighting.
Result: Their games were all massively adopted by the buying public because nearly every game had a rig capable of handling them. This is especially important in regard to their success among the new south-asian middle class.
Another reason not to ride the bleeding edge is the demand on the various designers and artists responsible for creating the content to match the game engine.
This has led to the somewhat sad trend within FPS'es where the games get steadily shorter and more railroaded because the developers does not have time and resources to map out extensive worlds to match the bloated specs.
Or, another example, why do so many people still map for Doom? Because Doom mapping is relatively easy to get into and a Doom map can be made or worked on in your spare time without requiring extreme dedication or an education as a computer graphics artist. Every averagely computer literate person could potentially get into Doom mapping.
Finally developers can use more time to develop compelling art and settings and genuinely fun game mechanics, and can be more daring in doing so, because they don't have to sink resources into learning new advanced tech and use copious hours doing bloated resource files such as high-polygon photorealistic models.
Look at the wealth of titles put out for the handheld consoles such as PSP and DS as well as the "quirky" console Wii. We have stuff such as "Phoenix Wright: Ace Attourney" an excellent idea, masterfully executed, but possessing outright primitive graphics. Or LocoRoco, arguably the cutest video game ever (and one of the best soundtracks ever).
Meanwhile those working with the newest tech produce formulaic FPS'es and RTS'es Cutscene-whore Final Fantasy episodes and bad Hollywood tie-ins.
So by sticking with yesterdays tech you are more likely to get games with:
A large following, important for multiplayer games and is a factor in their longevity.
More focus on content, potentially longer games, with more potential fan-made content. Better, more thought out content.
More "daring" games willing to challenge the genre status quo.
More focus of straight ahead gameplay. IE, streamlined deathmatch-FPS'es, good, ol' arcadey fun, strategy games with a focus on strategy.
And finally, you don't need to rely on going out and blowing your money on the latest graphics card all the time.