Is there a reason why the DVD versions weren't in widescreen? I read a post on DS explaining that if an old US show was released on DVD, it'd be taken from the master copy rather than the tape used by broadcasters that wears over time.
Because the show master tapes were 4:3 until very recently. Its only as new rights deals have been signed (or old ones renewed / renegotiated) that the HD versions have appeared. Presumably Warner Bros realised the demand and, as it was possible, spent the time and money creating them.
You'd think they'd want to cash in by releasing the 'remastered' versions on DVD and Blu-Ray, although they may feel that, currently, those buying the DVDs are happy with the 4:3 versions, particularly as the current releases are extended edits, rather than those cut to time for broadcast. (As well as the fact that most people will be stretching the 4:3 picture on a 16:9 set and don't realise / won't care.) It may be that over time, as people see the HD versions on TV they'll expect to be able to buy them. From the screen grabs I've seen it appears theres a big improvement over the old mater copies- which never were very good.
Warner are being quite slow in releasing TV shows on Blu-Ray. There are HD versions of ER and The West Wing which have been shown / made available elsewhere (ER on TV, TWW on HD download) but have yet to be released to buy on disc.