The original theatrical versions were released on DVD as bonus discs to a re-release of the special editions, but they were bad letterboxed transfers from the same master as the laserdisc version. So the original versions have been released on DVD, but it was half-assed at best.
Ah, that rings a bell now. That's right, from the Laserdisc transfer.
OK, they haven't been released in a vaguely good viewable version on DVD.
And frankly, the fact that it was the Laserdisc transfer that was used in the first place doesn't speak well of the current status of the original print, especially given what we know of the headaches involved in producing the Special Editions.
Do we really need the originals, though? They should just release a "Shittiness Reduced" version. Put a CGI Shaw back in RotJ's ending, edit out the godawful dance scene in Hutt's palace, mute Vader's "NOoooOOOoo", put the original Krayt Dragon scream back in ANH and you have a decent version again.
I don't think I'm missing anything.
Edit: How could I forget one of the biggest ones? Have Han pew-pew Greedo first.
You're missing quite a bit, ranging from minor to major. Lots of replaced background mattes or entirely new establishing shots, tweaked colouring, the infamous Greedo shooting first (and obviously ditch the awful Jabba scene from ANH), replacing many of the space shots with new CG ones, replacing all of Boba Fett's dialogue with that NZ guy, new creatures and characters added to many shots, badly changing the lightsaber colours, removing Vader's eyebrows, adding rocks to hide R2, so many other random CG elements added for no reason, replacing the emperor.
A lot of the changes are just fine or an improvement, but there are just as many that were unnecessary and silly, and don't match the original film.
While I don't have a problem with them mixing and matching in theory, a lot of people just want to see the original theatrical cut as they grew up with pre-SE, not to mention it would be a travesty not to preserve the original unaltered version of such a huge film for posterity. Keep "Ep IV: A New Hope" in the opening crawl, keep the fixes to the blue screen effects and matte box problems, but otherwise just release a clean version of the movie. Then they can still release their new version as Lucas says he always intended without people complaining. Two versions of the movie is fine. Then if fans want some kind of inbetween hybrid, they can sort it out.