Where have you been?? It's been out on DVD for 15 damn years!! If you want DVDs rather than Blurays, you're in luck because for once, there are basically zero new extras for the Blurays, it is all stuff ported over from the various DVDs. People are getting it because they specifically wanted Blurays- it's not that The X-Files had never been released before- all the content is already on DVD.
Also, with the Blurays now being out, lots of people who are getting the Bluray are probably going to be selling their DVDs. Go on Amazon marketplace (or whatever we call the third party sellers on Amazon) or ebay and look for the XF DVDs, you should be able to get them super cheap in a like-new or very-good condition. Granted, you will have to pick up the mythology DVD sets as well (a set of compilations focusing only on mythology episodes) if you want ALL the extras that are on the Blurays, because the mythology sets contain a lot of unique commentary tracks and a few documentaries that aren't on the regular DVDs (which have their own different extra features). The Blurays provide all these extras together on the discs, but for the most part, unless commentaries on mytharc eps matter greatly to you, you should be fine with the regular DVDs. Also there may be one or two very minor new features on the Blurays that haven't been announced, I don't know, or possibly some easter eggs. But ALL the announced content on the Blurays- all the episodes in uncut form obviously, and also the extras- are on the DVDs.
Finally, there is even another reason to own the DVDs- it is now the only way to see the show in its original intended form. The Blurays offer a new HD version, which is something that needed to happen, but unfortunately, the technicians created two alternate HD versions- one version, approved by the show's creators, includes season 1-4 in its original screen ratio of 4:3, the other version, not really approved by them, has been converted to 16:9- and Fox (who, unlike the creators, owns the rights and can do whatever they want with it) wanted to release the 16:9 version for all seasons, and that is what they've done with the Bluray. This is obviously a wise move commercially for Fox, because 16:9 HD is the most popular media format right now, and there isn't quite as much market for something like 4:3 HD, even if 4:3 is the original format intended by the creators for seasons one to four of this particular show. The technician who worked on the HD versions specifically said they worked on both, and it looked really beautiful in HD in its original 4:3 compositions, but Fox wanted them to do an edited 16:9 version as well and that was the only one Fox released.
People can argue over the merits of chopping up older media to different sizes to fit current trends, especially in complicated cases like this where the original show WAS shot on wider-than-4:3 film that, in some shots (ONLY some shots), allowed them to add new material on the sides while they deleted material from the top and bottom of the original (in many other shots they deleted material without adding anything- also, when they did add material, it was material that was there on the film but was not intended by the director or producers to ever be seen). Anyway, when it entails losing entire shots out of the original (something the technicians involved in the HD conversion have said was necessary) and when the creator of the show specifically said he wanted them not to do that, and when in addition to other changes, they made obvious (and most fans agree, rather weakly executed) changes to the on-screen fonts used in the credits and taglines, and even changed the songs heard in the soundtrack in certain important episodes... well... a LOT of changes were made that do not necessarily improve anything- and were only made for practical reasons because the technicians, asked to convert one format to another, had no choice but to do it- in fact, Fox should never have asked them to do that.
Movies that are taken seriously as art are not "converted" this way, just like black and white movies are no longer "colorized." When you try to "improve" older media by chopping and screwing with it until it looks exactly like newer media, you throw the baby out with the bathwater (to use a super old expression) and miss the point of why newer audiences are interested in checking out the classics in the first place. Nobody is going to think X-Files is a brand new show created in the 2010s, no matter how crisp the HD, no matter if they chop it up to be in 16:9. So it's a losing game to try to pretend it's something it isn't. They needed to OWN IT the way it is- it's a 4:3 show in season 1-4, but that doesn't make it any less artistic- many of the greatest films ever made are in 4:3 (and have never been "converted" to 16:9 for their own Bluray releases, which are only available in 4:3 HD). Twin Peaks, the only show that's even more cinematic (at times) than The X-Files, is on Bluray in a perfect, pristine 4:3 HD restoration personally approved by David Lynch. This is how you do TV on Bluray if you care about art. Some companies, of course, treat the shows they release simply as a money making tool, disrespecting the artists behind it, and condescending to the fandom.
The 16:9 versions are an interesting novelty- and they are creator-approved for season 5-9. But if seasons 1-4 are favorite seasons of yours, it is at least a good idea to have access to the original versions of those seasons via the DVDs (sadly not in HD- although Fox HAS in their vault perfectly restored HD versions they just haven't wanted to put out).