I don't understand why. Do you only want DRM-free retail releases? Or do you want DRM free retail games? Also that there are so many of them should not be a problem but a source of happiness. Isn't it fine that we can now have so many DRM-free games on retail also as re-releases. I would add as many as possible. Maybe one could sort by year of original release. Maybe one could also put this list on the GOG-Wiki.
Oh, it's definitely a good thing. But the thing is, if I start including every pre-2008 game by virtue of their being DRM-free, the list will get very long and very unmanageable, so it's better to keep it to the games whose DRM freedom is not so apparent.
It should be obvious to all here that the vast majority of retail releases pre-2008 - with minor exceptions such as Half-Life 2 and Earth 2160 - are DRM-free.